There are thousands of periodic tables in web space, but this is the only comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Dr Mark R Leach.
Use the buttons below to select from the 1000+ Periodic Tables in the database:
Periodic Tables providing data about the chemical elements, rather than novel formulations:
There are 94 naturally occuring elements, from hydrogen to plutonium. Together they make up everything in the world.
94 Elements is a global filmmaking project, exploring our lives through the lens of the elements. Everything that surrounds us is made from these 94 building blocks, each with its own properties and personality. Our own bodies are mostly made from just 6 of them.
The stories of the elements are the stories of our own lives. They reveal the patterns of our economies and the state of our relationships with our natural resources. The project is in part a celebration of the art of documentary film and some of the best filmmakers working today are making new films for the project. There'll also be opportunities for talented new and emerging filmmakers and animators to pitch their own films, with the winners chosen by you - the project community.
A 1970 periodic table by Prof. Wm. F. Sheehan of the University of Santa Clara that claims to show the elements according to relative abundance at the Earth's surface. [However, we dispute the relative areas given to the various elements; there is almost no helium at the Earth's surface, for example.] Click the image to enlarge:
Below are some cartiogram representations, including the relative abundance of the elements in the Earth's crust, from Mark Winter's WebElements website:
Acid-Base Behavior of 100 Element Oxides: Visual and Mathematical Representations by Mikhail Kurushkin and Dmitry Kurushkin. J. Chem. Educ. 95, 4, 678-681.
A novel educational chart that represents the acid-base behavior of 100 s-, p-, d-, and f-element oxides depending on the element's electronegativity and oxidation state was designed. An updated periodic table of said oxides was developed. A mathematical criterion based on the chart was derived which allows prediction of the behavior of unfamiliar oxides:
Eric Scerri has supplied two periodic tables showing "anomalous configurations for gas phase atoms, highlighted in yellow, and for condensed phase atoms, purple." (The f-block anomalies for condensed phase are yet to be calculated.)
One of several animations and explanations/realisations of quantum physics
from Data-Burger, scientific advisor: J. Bobroff, with the support of: Univ. Paris Sud, SFP, Triangle de la Physique, PALM, Sciences à l'Ecole, ICAM-I2CAM.
Mark Leach writes:
"What I particularly like about this video is that it shows the quantum fuzziness of the atoms. This explains/shows how and why induced-dipole/induced-dipole (London force) interactions occur, an important class of van der Waals interaction. At any moment, the electron distribution is not perfectly spherical, which means that there is an instantaneous dipole on the atom. This instantaneous dipole is able to induce a dipole on an adjacent atom, with the effect that the two atoms are attracted when they touch. It is as if atoms are 'sticky' like Velcro.
"This effect explains why the Group 18 noble gas elements are able to form liquids and solids [not He] at low temperatures, and why non-polar molecules, such as P4, S8 and hydrocarbons are able to condense."
By Leland Allen, a representation of the periodic table with the third dimension of energy derived from the averaged ionisation potentials of the s and p electrons. (Allen suggested that this was a direct measure of electronegativity). From J. Am. Chem. Soc. 1989, 111, 9004:
Baker's electronegativity table of 1870 differs from Berzelius' listing of 1836 only by the addition of the newly discovered elements. Page 280 and ref. 5 from Bill Jensen's: Electronegativity from Avogadro to Pauling Part II: Late Nineteenth- and Early Twentieth-Century Developments, J. Chem. Educ., 80, 279-287 (2003):
The most electronegative element (oxygen or Sauerstoff) is listed at the top left and the least electronegative (potassium or Kalium) lower right. The line between hydrogen (Wasserstoff) and gold seperates the predomently electronegative elements from the electropositive elements. Page 17 and ref. 32 from Bill Jensen's Electronegativity from Avogadro to Pauling Part I: Origins of the Electronegativity Concept, J. Chem. Educ., 73, 11-20 (1996):
A periodic table showing where
biologically essential (green), essential trace (purple), toxic (red),
radioactive (yellow) and of low but not zero biological impact
(gray) elements are found. Only highly toxic elements are shown in red.
Li (as Li+) is biologically active and is used as an antidepressant.
"I believe that the progress of science made in these last years has confirmed the hypothesis of Avogadro, of Ampère, and of Dumas on the similar constitution of substances in the gaseous state; that is, that equal volumes of these substances, whether simple or compound, contain an equal number of molecules: not however an equal number of atoms, since the molecules of the different substances, or those of the same substance in its different states, may contain a different number of atoms, whether of the same or of diverse nature."
"In 1858 Cannizzaro outlined a course in theoretical chemistry for students at the University of Genoa,where he had to teach without benefit of a laboratory. He used the hypothesis of a fellow Italian, Amedeo Avogadro, who had died just two years earlier, as a pathway out of the confusion rampant among chemists about atomic weights and the fundamental structure of chemical compounds."
Mark Leach writes:
"Before a periodic table of the chemical elements – which orders the elements by atomic weight and then groups them by property – could be developed it was necessary to know the atomic weight values. However, to deduce the atomic weights was a problem as it was necessary to know the ratios of how the elements combined, the stoichiometry.
"Tables of atomic weight data by Dalton (1808), Wollaston (1813) and Daubeny (1831) show progress, but the 1858 Cannizzaro letter was the first where the atomic weight data is more or less both complete and accurate.
"I have extracted the element atomic weight data from the paper, and given the % error with respect to modern atomic weight/mass data. Only titanium is significantly out! It is clear that Cannizzaro knew that hydrogen, nitrogen, oxygen, chlorine, bromine & iodine existed as diatomic molecules."
Webelements have produced a poster with various atomic & elemental properties represented in cartographic form. From the Webelements shop:
"Periodic table cartograms are periodic table grids distorted using a computer algorithm so that the areas of the element squares are in proportion to a periodic table property. This is the first poster to show periodic properties plotted in this way".
This collaborative periodic table is designed by chemistry students from all Canadian provinces and territories, 20 US states and 14 different countries. Chem 13 News readers registered their chemistry students to artistically interpret one element. Combined these tiles form one innovative and unique periodic table. A poster of the table and a traveling display are currently being constructed.
Guillermo Restrepo, MPI for Mathematics in the Sciences:
"A periodic table of chemical bonds: Each of the 94 circles with chemical element symbols represents the bond that the respective element forms with an organic residue. The bonds are ordered according to how strongly they are polarized. Where there is a direct arrow connection, the order is clear: Bonds of hydrogen, for example, are more polarized than bonds of boron, phosphorus, and palladium. The same applies to rubidium in comparison to caesium, which has particularly low polarized bonds and is therefore at the bottom of the new periodic table. If there is no direct arrow between two elements, they may still be comparable – if there is a chain of arrows between them. For example, the bonds of oxygen are more polarized than the bonds of bromine. Bonds represented by the same colour have the same binding behaviour and belong to one of the 44 classes.":
"The periodic table of chemical elements as a collection of images [click to zoom in]. A collection of images of materials constitute the basic components of the whole universe. This is a periodic table of chemical elements (also called short PSE) with a difference! Visible in pure form, as it really looks like. Not only naked dry boring data. There are the alkali metals, alkaline earth metals, boron group, carbon group, nitrogen group, chalcogens, halogens, noble gases, hard metals, ferrous metals, precious metals, lanthanides..." from the website, here:
A quote neatly sums up what the ChemThes reaction chemistry database project is trying to achieve:
"The Chemical Thesaurus is a reaction chemistry information system that extends traditional references by providing hyperlinks between related information. The program goes a long way toward meeting its ambitious goal of creating a nonlinear reference for reaction information. With its built-in connections, organizing themes, and multiple ways to sort and view data, The Chemical Thesaurus is much greater than the sum of the data in its database.
"The program does an excellent job of removing the artificial barriers between different subdisciplinary areas of chemistry by presenting a unified vision of inorganic and organic reaction chemistry."
"We have developed a visual periodic table that groups by orbitals, making He no longer contentious. But by including an orbital cloud, we give the student a great offset to the Bohr model used to place each and every single electron in the periodic table."
Twelve elements were known from the Ancient Times, and were described by Romans and Greeks. The remaining 106 elements have been discovered by scientists of 15 different countries during the last 4 centuries. In addition, 19 elements of those 106 (18%) have been co-discovered by researchers of two countries.
Although some of them (like Bromine or Thallium) were isolated separately at the same time by chemists of different nationalities within the race to discover new elements in 18th-21st centuries, most of them have been obtained since then through collaborative research, like the recently discovered Ununpentium, Ununseptium and Ununoctium.
Another example is the isolation of Radium and Polonium by the Polish Maria Skłodowska-Curie and her French husband, Pierre Curie.
Thus, Periodic Table is the result of a collective and long-term work of hundreds of scientists.
It is noteworthy to see that Russia and United States have discovered mainly artificial elements.
Compilation of Minimum and Maximum Isotope Ratios of Selected Elements
Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry.
This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope abundance variations potentially are large enough to result in future expansion of their atomic weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope-abundance variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic weight uncertainties.
Compilation of Minimum and Maximum Isotope Ratios of Selected Elements in Naturally Occurring Terrestrial Materials and Reagents
Two pages from John Dalton's A New System of Chemical Philosophy in which he proposed his version of atomic theory based on scientific experimentation (see the scanned book, page 219):
Dalton states that he is considering "chemical elements or ultimate particles"
Dalton assigns hydrogen as having a relative weight of 1.
Note the seemingly huge % errors in the atomic weights, compared with modern values.
These errors occurred because while Dalton had deduced that atoms combine in fixed (stoichiometric) ratios in compounds, he not always know what the ratios were. Thus there were two unknowns: the atomic weights (masses) and the stoichiometric ratios.
Daubeny's Teaching Display Board & Wooden Cubes of Atomic Weights
The Museum of the History of Science, Oxford, has a display of Charles Daubeny's teaching materials, including a black painted wooden board with "SYMBOLS OF SIMPLE BODIES": showing symbols, atomic weights and names of elements in two columns, and a small pile of cubes with element symbols.
Charles Daubeny and Chemistry at the Old Ashmolean
Charles Daubeny (1795-1867) was appointed Aldrichian Professor of Chemistry at Oxford in 1822. In 1847 he moved from the original laboratory in this basement [in the museum] to a new one built at his own expense at the Botanic Garden. His apparatus went with him and was preserved there.
Daubeny actively campaigned for the teaching of science in Oxford and held several professorships in addition to chemistry. He also conducted research on subjects such as photosynthesis.
DAUBENY'S LIST OF ATOMIC WEIGHTS Wooden panel, black with white lettering, listing in two columns the symbols and names of twenty elements. This lecture board is identical to the table in the third edition (1831) of E. Turner, 'Elements of Chemistry', apart from the atomic weight for bromine. Daubeny wrote a useful 'Introduction to the Atomic Theory' (published in three versions: 1831, 1840, and 1850), the first edition of which also quotes Turner's table. Probably contemporary with this lecture board are the wooden cubes with the symbols for certain elements.
The period from 1810 to 1860 was crucial in the development of the periodic table. Most of the main group and transition elements had been discovered, but their atomic weights and stoichiometries (combining ratios) had not been fully deduced. Oxygen was assumed to have a weight of 6, and consequently carbon is assumed to have a mass of 6.
Daubeny's element symbols and weights – along with the modern mass data – are tabulated:
Modern Mass Data
factor of 2
factor of 2
factor of 5 (?)
factor of 3
factor of 2
factor of 2
factor of 2
factor of 2
factor of 2
factor of 2
While quite a number of weights are close to the modern values, many are way out. However, the error is usually a stiotoimetric factor error.
Forty-two wooden cubes numbered 1-42, painted black with symbols for certain elements, compounds or radicals painted in white on the faces, together with the corresponding atomic, molecular or radical weights. The face markings appear in various combinations:
A typical cube (no. 3) may be represented by the following figure. They present something of an enigma as their faces do not form an obvious pattern. The numbers indicate that there were 42 cubes. In style they are similar to the figures on the panel of atomic weights.
The cubes are listed in Daubeny's 1861 catalogue, p. 11 as: "Wooden cubes for illustrating atomic weight".
[See D. R. Oldroyd, The Chemical Lectures at Oxford (1822-1854) of Charles Daubeny, M.D., F.R.S. Notes and Records of the Royal Society, vol. 33 (1979), pp. 217-259.]
This display was spotted by Eric Scerri who was visiting the museum with Mark Leach in 2010.
From Mark R Leach's paper, Concerning electronegativity as a basic elemental property and why the periodic table is usually represented in its medium form, Journal & PDF.
Due to the importance of Pauling's electronegativity scale, as published in The Nature of The Chemical Bond (1960), where electronegativity ranges from Cs 0.7 to F 4.0, all the other electronegativity scales are routinely normalised with respect to Pauling's range.
When the Pauling, Revised Pauling, Mulliken, Sanderson and Allred-Rochow electronegativity scales are plotted together against atomic number, Z, the similarity of the data can be observed. The solid line shows the averaged data:
A periodic table showing electronegativity,
"The ability of an atom to attract electron density from a covalent
bond" (Linus Pauling). Blue elements are electronegative,
red elements are electropositive, and purple
elements are intermediate. Notice how hydrogen is intermediate
in electronegativity between carbon and boron and is positioned above
and between these elements:
"Scientist in Berkeley discover new elements [Californium & Einsteinium] from hydrogen bomb debris in 1951 and then use the 60 inch Cyclotron to create Mendelevium, element 101. The team included Nobel Prize winner Glenn Seaborg and famed element hunter, Albert Ghiorso."
The event, chaired by MEPs Catherine Stihler and Clare Moody, presented an encompassing overview of what element scarcity means for us: both on a scientific level, but also economically and politically. A presentation from speaker Natalia Tarasova, IUPAC Past President, contextualised EuChemS' work within the celebrations of the International Year of the Periodic Table, whilst M Pilar Gil, from the University of St Andrews, delivered a remarkable and exhilarating talk on how the recently discovered oldest known wallchart of the Periodic Table was uncovered and dated.
"Red indicates that dissipation will make the elements much less readily available in 100 years or less: helium (He), silver (Ag), tellurium (Te), gallium (Ga), germanium (Ge), strontium (Sr), yttrium (Y), zinc (Zn), indium (In), arsenic (As), hafnium (Hf) and tantalum (Ta).
"Helium is used to cool the magnets in MRI scanners and to dilute oxygen for deep sea diving. Vital rods in nuclear reactors use hafnium. Strontium salts are added to fireworks and flares to produce vivid red colours. Yttrium is a component of camera lenses to make them shock and heat resistant. It is also used in lasers and alloys. Gallium, meanwhile, is used to make very high-quality mirrors, light-emitting diodes and solar cells."
or Salt-Like Hydrides: Molten LiH conducts
electricity and hydrogen gas is liberated at the anode confirming presence
of hydride ion H. The crystal structures show an ionic
lattice, and not an LiH molecular lattice.
are formed by the p-Bolock elements.
Interstitial Hydrides are formed by many d-block and f-block elements
when heated with hydrogen under pressure. The hydrides tend to be non-stoichiometric
and they may be of variable composition.
There is a Hydride
Gap where elements do not form hydrides. This roughly maps to the
Siderophile Elements of the geologist's periodic table (below).
Hydrides do not fit: beryllium hydride is polymeric, (BeH2)n.
Others have properties between metallic and covalent.
The main group elemental hydrides
are all well known reagent chemicals. The main group hydrides always give
the lowest and most common oxidation state, and all chemicals are molecular
in the gas phase. The Group I and II hydrides are ionic materials, but
they can be vaporised to give the molecular form.
The chemicals present and behave
as Lewis acids, Lewis bases or Lewis acid/base complexes, here:
The periodic table of fluorides
(mainly) shows the range of possible oxidation states. Note that lithium,
by way of example, is deemed to have two oxidation states: Li0
(the metal), and Li+ (the lithium ion):
There are a few exceptions
and points to note:
There is a general increase
in the number of possible oxidation states towards the lower right hand
side of the periodic table.
Nitrogen(V) fluoride, NF5,
is not known, but the nitrogen(V) oxide is: N2O5.
and PtBr3 are known, but PtF2
and PtF3 are not.
All elements are known in
the zero oxidation state, but apart from: He, Ne & Ar, and these
are not shown in the diagram below.
Elements: A Series of Business Radio Programs/Podcasts
A series of BBC World Service Radio Programs, available as MP3 Podcasts, talking about the chemical elements with a strong business/technology bias, rather than the more usual chemical or historical approach:
Prepared by P. Lof is Elsevier's Periodic Table of the Elements.
This educational wall chart features the periodic table of the elements supported by a wealth of chemical, physical, thermodynamical, geochemical and radiochemical data laid down in numerous colourful graphs, plots, figures and tables. The most important chemical and physical properties of the elements can be found - without turning a page.
All properties are presented in the form of tables or graphs. More than 40 properties are given, ranging from melting point and heat capacity to atomic radius, nuclear spin, electrical resistivity and abundance in the solar system. Sixteen of the most important properties are colour coded, so that they may be followed through the periodic system at a glance. Twelve properties have been selected to illustrate periodicity, while separate plots illustrate the relation between properties. In addition, there are special sections dealing with units, fundamental constants and particles, radioisotopes, the Aufbau principle, etc. All data on the chart are fully referenced, and S.I. units are used throughout.
Designed specifically for university and college undergraduates and high school students, "Elsevier's Periodic Table of the Elements" will also be of practical value to professionals in the fields of fundamental and applied physical sciences and technology. The wall chart is ideally suited for self-study and may be used as a complementary reference for textbook study and exam preparation.
standard atomic weight
ground-state electronic configuration
discoverer and year of discovery
melting point; boiling point
molar enthalpy of atomization
molar enthalpy of fusion
molar enthalpy of vaporization
atomic energy levels of the outermost three orbitals
formal oxidation states
selection of standard reduction potentials
first, second & third molar ionization energies
molar electron affinity
polymorphic transition temperatures
effective ionic radii
volumic mass (density)
abundance in the solar system
abundance in the Orgueil meteorite
abundance in the solar photosphere
abundance in the continental crust
abundance in the primitive mantle
abundance in the oceanic crust
naturally occurring isotopes
mass number and representative isotopic composition
molar heat capacity
coefficient of linear thermal expansion
price; annual mining production
world reserve base
nuclear spin and NMR receptivity
Mossbauer active nuclides
physical (standard) state
abundance in food (human daily intake)
principal hazardous property
Other information: Aufbau principle, quantum numbers, orbitals and sequence of orbital filling; trivial group names; drawings of crystal lattice structures; 12 plots of a chemical/physical property against atomic number; 9 plots of a property against another property; list of SI units and SI prefixes; list of other units and their conversion to SI; list of fundamental physical constants; scheme of fundamental particles; list of radioisotopes with half-life longer than 5 days, presenting half-life and mode(s) of decay, indicating cosmogenic isotopes and isotopes produced by U-235 fission, as well as radioisotopes used in geochronology, pharmacology and nuclear medicine.
First Ionisation Energy to the Standard Form Periodic Table
There is debate amongst the cognoscenti about the 'best' representation of the periodic table, and how this 'best' formulation can be explained by [rationalized by] quantum mechanics (QM).
Many feel that the Janet PT formulation, the 'Left Step', is the ideal QM PT, but this formulation does not show periodicity very well, and there are issues with the placement of H, He, Be which spill over into questions about their placement in the standard form PT (the periodic table used in classrooms and textbooks around the world).
However, it is possible to get to the conventional standard form PT directly from the first ionisation energy data, where the 1st ionisation energy is the energy required to convert a gas phase atom (M) into its gas phase positive ion plus electron.
M(g) → M+(g) + e–
The process involves:
taking the 1st ionisation data plot for the elements H to Xe (Z = 1 to 36)
rotate 90° clockwise and stretch
move the atoms horizontally into columns
Note that a similar logic can be applied to atomic radius and electronegativity data.
Elements - noble gases and covalently bonded
gaseous molecules. The atoms and molecules are attracted by weak van
der Waals forces and so these elements remain gaseous at room temperature.
- Those elements which form ionic bonds generally have filled outer
electron shells. They typically bond to oxygen in silicates and oxides.
- The metals near iron in the periodic table that exhibit metallic bonding,
have a weak affinity for oxygen and sulfur and are readily soluble in
molten iron. Examples include iron, nickel, cobalt, platinum, gold,
tin, and tantalum. These elements are depleted in the earth crust because
they have partitioned into the earth's iron core.
- The elements that bond to S, Se, Te, Sb, and As. These bonds are predominantly
covalent in character.
The figure below shows the subshell strings aligned in columns based on the total pool of valence electrons as described above. This is the global periodic table. Each column constitutes a global group. Each term in column 1 launches a global period. The global periodic table is a purely mathematical matrix that assigns precise row and column coordinates to all positive integers but makes no predictions as to the order in which subshells are filled. Read more here.
Theodore Gray's Periodic Table.Com is a live version of what is generally regarded as the most beautiful
periodic table to be developed so far. It is a treasure trove of pictures, videos and stories. Explore!
Theo is an enthusiast and a collector, and he uses the power of Mathematica (he is a co-founder of Wolfram Research) to drive his astonishing website. It is Theo's aim to be the number one periodic table resource on the web.
Mark Leach, the database curator writes:
"I find Theo's website and approach to be complementary to the more academic WebElements."
There are several ways in which the 'common/modern medium form' periodic table are shown with respect to the Group 3 elements and how the f-block is shown. Indeed, there is even some dispute about which elements constitute Group 3.
"Introducing the world's first and only miniature Periodic Table with the actual elements in it.
"Over the last year, we have successfully collected each and every stable element. After considerable R&D, we have finally developed a method of embedding each element in acrylic and we have to say, the result is awesome!
"The Heritage Periodic Table pretty much speaks for itself. The collection looks great on a desk, in your hands, and anywhere else it can be displayed."
"About 60 miles southwest of Las Vegas, in a mine some 500 feet deep, the beginnings of an iPhone come to life.
But the sleek, shiny iPhone is far, far removed from the rocks pulled out of this giant hole, which looks like a deep crater on the moon. Inside the rocks from this mine are rare-earth minerals, crucial ingredients for iPhones, as well as wind turbines, hybrid cars, and night-vision goggles. Minerals such as neodymium are used in magnets that make speakers vibrate to create sound. Europium is a phosphor that creates a bright red on an iPhone screen. Cerium gets put into a solvent that workers use to polish devices as they move along the assembly line, etc.":
By Jordi Cuadros, a set of three pairs of periodic tables in Catalan, English & Spanish pointing out the differences between PT representations of atoms and PT representations of the material substances:
From Wikipedia: The island of stability in nuclear physics describes a set of as-yet undiscovered isotopes of transuranium elements which are theorized to be much more stable than others. The possibility was proposed by Glenn T. Seaborg in the late 1960s: Prospectd for Further Considerable Extension of the Periodic Table, J.Chem.Educ., 46, 626-633 (1969) and reprinted in Modern Alchemy: Selected Papers of Glenn T. Seaborg (1994).
The hypothesis is that the atomic nucleus is built up in "shells" in a manner similar to the structure of the much larger electron shells in atoms. In both cases, shells are just groups of quantum energy levels that are relatively close to each other.
The 1 Dec 2018 IUPAC (International Union of Pure and Applied Chemistry) Periodic Table of The Elements. For updates to this table click here.
By virtue of its work in relation with the chemical elements, IUPAC can dispense a periodic table that is up-to-date. IUPAC involvement covers various aspects of the table and data that it unveils, and several reports and recommendations, some quite recent, attest of that input.
In particular, IUPAC is directly involved in the following:
establishing the criteria for a new element discovery
defining the structure of a temporary name and symbol
assessing claims resulting in the validation and assignation of an element discovery
coordinating the naming of a new element, involving the research laboratory and allowing for public comments
setting up precise rules for how to name a new element
The Periodic Table of the Isotopes, published by International Union of Pure and Applied Chemistry (IUPAC), is now available from the Commission on Isotopic Abundances and Atomic Weights, which is a commission under the Inorganic Division (Division II) of IUPAC.
The text identifies four types of atom, with respect to isotopes:
Element has two or more isotopes that are used to determine its standard atomic weight. The isotopic abundances and atomic weights vary in natural terrestrial substances. These variations are well known, and the standard atomic weight is given as lower and upper bounds within square brackets, [ ].
Element has two or more isotopes that are used to determine its standard atomic weight. The isotopic abundances and atomic weights vary in natural terrestrial substances, but upper and lower bounds of the standard atomic weight have not been assigned by IUPAC or the variations may be too small to affect the standard atomic weight value. Thus, the standard atomic weight is given as a single value with an uncertainty that includes both measurement uncertainty and uncertainty due to variations in isotopic abundances.
Element has only one isotope that is used to determine its standard atomic weight. Thus, the standard atomic weight is
invariant and is given as a single value with an IUPAC evaluated measurement uncertainty.
Element has no standard atomic weight because all of its isotopes are radioactive and, in natural terrestrial substances, no isotope occurs with a characteristic isotopic abundance from which a standard atomic weight can be determined.
For the iPhone and iPad, JR's Chemistry Set makes chemistry interesting and fun to learn. Based upon the innovative Rota Period, it is a handy and powerful reference tool for chemistry enthusiasts and practitioners at all ages and all levels.
The procedure involved plotting the data, rotating 90°, squeezing vertically and smoothing. The points need a little tidying up, and then they can be mapped directly onto the Seaborg formulation periodic table.
The only element which does no obviously 'line-up' with the periodic table is hydrogen, but many modern periodic tables have H floating as it is not obvious if it should be considered to be a Group 1 alkali metal or a Group 17 halogen.
There are advantages and disadvantages to each data set. The 1st ionisation energy data from NIST is known with up to seven significant figures of precision, but the data jumps about at times due to the presence of the s & p-orbitals, which appears to make the data a little noisy. (Actually, this 'noise' is embedded information about the electronic structure of the atoms.) The atomic radius gives smoother data, but as gas phase atoms do not have hard edges calculated (Clementi 1967) rather than experimental values, must be used.
In his book Concise Inorganic Chemistry (pp. 22, 5th Ed, Blackwell Science, 1996), J.D. Lee gives a representation of "Quantum numbers, the permissible number of electrons & the shape of the periodic table".
Note: JD Lee taught Inorganic Chemistry to the curator of this database of periodic tables while at university:
The book lists the several hundred chemicals known at the time, including chemical elements, and it discusses the nomenclature (naming). Although not a periodic table as such, the information contained in this book was state of the art for 1787.
Pairs of atoms where atomic
mass does not follow atomic number.
quirk due to the intricacies of nuclear chemistry and isotopic
abundance caused no end of difficulties to the developers of
the periodic table in the mid-nineteenth century. Scientists could determine
atomic mass, but knew nothing of protons or atomic numbers.
anomaly was a particular problem.
All of the the main group elements
are common laboratory reagents or chemical in bottles. They
appear as metals, metalloid (semi-metals) and non-metals. Most of the
non-metals are molecular materials while most of the metalloids have an
extended network-covalent structure.
Elsewhere in the chemogenesis
web book, material type is discussed in terms of the Laing
Tetrahedron, an analysis that classifies binary materials in terms
of four extreme types: metallic, ionic, molecular and network. However,
none the chemical elements present as ionic materials, only as metals,
molecular (van er Waals) and network materials:
The elements B,
C, Si, P, S, Ge, As, Se, Sn, Sb and Te can form allotropes: pure elemental
substances that can exist with different crystalline structures from
Allotropes may be metallic, network or molecular.
From the paper, specifically the text associated with the figure:
The periodic table with known medicinal uses of each main group or transition metal element when available. In the following, we list the use of each element.
Hydrogen (H), boron (B), carbon (C), calcium (Ca), phosphorous (P), potassium (K), magnesium (Mg), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), selenium (Se), rubidium (Ru), molybdenum (Mo), and cesium (Cs) are commonly found in supplements readily available to the public and are illustrated as such. Helium (He) is crucial in the operation of MRI machines.
Lithium (Li) as lithium carbonate is the most common treatment of bipolar disorder.
Beryllium (Be) foil is used as shielding in radiographic instruments.
Nitrogen (N), as nitrous oxide, is a common anesthetic.
Oxygen (O) has many medical uses, including anesthetics and resuscitation, and is illustrated here for use in ventilation.
Fluorine (F) and tin (Sn) as stannous fluoride are a common ingredient in toothpaste.
Sodium (Na) and chlorine (Cl) are used as NaCl in saline solutions.
Aluminum (Al) compounds are a common active ingredient in antiperspirant deodorants.
Silicon (Si) is used in antacid products.
Sulfur (S) is illustrated as campden tablets, which are used for sterilization in beer fermentation.
Argon (Ar) lasers are used in eye surgery.
Zirconium (Zr) is used in immuno-positron emission tomography (PET) imaging while scandium (Sc) is a candidate for the same technique.
Titanium (Ti), palladium (Pd), niobium (Nb), nickel (Ni), and tantalum (Ta) are used in medical implants.
Chromium (Cr) is shown as Cr(III) picolinate, which is a controversial supplement used in lowering insulin resistance.
Gallium (Ga), yttrium (Y), technetium (Tc), lanthanum (La), astatine (At), and actinium (Ac) are all used in nuclear medicine.
Arsenic (As), as As(III) trioxide, is used to treat certain forms of leukemia.
Bromine (Br) as KBr is an active ingredient in canine seizure medication.
Krypton (Kr) was used in lung ventilation studies but has since been phased out.
Strontium (Sr) is used in Sensodyne® toothpaste.
Rhodium (Rh), ruthenium (Ru), and rhenium (Re) complexes are used as anticancer agents.
Silver (Ag) is used in antibacterial ointments.
Indium (In) is used in white blood cell scans.
Antimony (Sb) is used in leishmania medicine.
Barium (Ba) is used in X-ray imaging of the gastrointestinal tract.
Tungsten (W) is used in shielded syringes.
Iridium (Ir) is used in brachytherapy.
Gold (Au) was used as a treatment for rheumatoid arthritis but has been phased out.
Mercury (Hg) is used in dental amalgams.
Lead (Pb) is used in X-ray aprons.
Bismuth (Bi) is used in stomach ulcer medicine.
Neon (Ne), germanium (Ge) cadmium (Cd), tellurium (Tl), hafnium (Hf), osmium (Os), polonium (Po), francium (Fr), radon (Rn), and radium (Ra) although most of these are toxic elements for human life, some of these elements are under development as potential agents for disease treatment but to our knowledge they are not currently used for beneficial applications in medicine.
"The element squares of this periodic table have colors resembling the actual colors of the elements. The table provides insight useful for helping to distinguish metals and non-metals as well as observations on elements of unusual color. The colors were taken from https://www.chemicool.com/ and applied with RGB codes."
"To celebrate the International Year of the Periodic Table of Chemical Elements, our editors have curated research papers, commentaries and multimedia from Nature and the Nature Research journals.
Dive in to find out what connects sodium with Sri Lanka, how many times astatine was discovered and where the White House got its name... And much more!"
Nagayasu Nawa, the prolific designer of periodic tables, here and here, has come up with an orbital filling periodic table and a corresponding hourglass animation. Nawa writes:
"I have turned the v.e.c. PT into the GIF animation that I call the electron
hourglass, 1 second for each element. It takes 120 seconds from 1H to
I have coloured orbital with colour derived from each shell's name, such as:
The range of NMR active nuclei observable on a particular instrument is, in part, a function of the configuration of the spectrometer and the choice of available probes. The periodic tables below identify the nuclei that have resonance frequencies within the detection range of the Lake Forest College Inova and the EFT-60 NMR spectrometers.
The nuclei in red are I=1/2 and yield spectra with narrow, non-overlapping resonances. The nuclei in blue have quadrapolar moments and may give rise to broad or very broad resonances in their spectra.
A PBS video explaining how neutron star mergers lead to the formation of heavy elements, and how a merger only 80 million years before the formation of the solar system, 4.5 billions years ago, seeded the Earth wth the heavy elements of the periodic table:
Today most element-building nucleosynthesis takes place in stars.
Stellar nucleosynthesis converts hydrogen into helium, either by the proton-proton chain or by the carbon-nitrogen-oxygen cycle. As a star evolves, a contracting superdense core of helium is produced from the conversion of hydrogen nuclei into helium nuclei.
Eventually, the temperature and pressure inside the core become high enough for helium to begin fusing into carbon. If the star has more than about twice the Sun's mass, a sequence of nuclear reactions then produces heavier elements such as oxygen, silicon, magnesium, potassium, and iron. Successively heavier elements, as far as iron (in the most massive stars) are built up in later stages of stellar evolution by the triple-alpha process. The heaviest elements of all are produced by explosive nucleosynthesis in supernova explosions, by mechanisms such as the p-process, r-process, and s-process:
Our quest to explain the origin of the elements started in the late 1950's by two famous papers independently - E. M. Burbidge et al., Rev. Mod. Phys. 29, 547 (1957) & A.G.W. Cameron, Pub. Astron. Soc. Pac. 69, 201 (1957) - whose authors claimed that the elements are created in astrophysical environments.
This is the well-known periodic table of elements, but where each element is labeled by the environment that is created (e.g Supernova explosion etc.).
In 2017 the LIGO gravitional wave detector identified the merger of two neutron stars, an event which produces large quantities of gold, platinum etc. Thus, an updated periodic table of nucleosyntheis looks like this, from an interesting SDSS blog:
Conal Boyce has prepared a Janet Left-Step Nucleosynthesis Periodic Table. Conal writes:
When plotting the number of stable isotopes against element, and against atomic number Z, it is clear that elements with an even atomic number are likely to have more stable isotopes (average 4.9) than elements with an odd atomic number (average 1.3). Click here for the Excel file. There is a Wikipedia page here.
The Oddo-Harkins rule holds that elements with an even atomic number (such as carbon) are more common than elements with an odd atomic number (such as nitrogen).
This effect on the abundance of the chemical elements was first reported by Giuseppe Oddo in 1914 and William Draper Harkins in 1917. See the Wikipedia page:
Students of chemistry are often confused why the orbitals fill with electrons: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6... etc., because the 3d10 seems to be 'out of sequence'.
This 'out of sequence' difficulity is nicely explained if the orbitals are arranged in a slightly different way:
The aufbau principle states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. For example, the 1s shell is filled before the 2s subshell is occupied. In this way, the electrons of an atom or ion form the most stable electron configuration possible.
The order in which these orbitals are filled is given by the n + rule, also known as the Madelung rule (after Erwin Madelung), the Janet rule or the diagonal rule.
Orbitals with a lower n + value are filled before those with higher n + values. In this context, n represents the principal quantum number and ? the azimuthal quantum number. The values = 0, 1, 2, 3 correspond to the s, p, d and f orbital lables.
Julio Gutiérrez Samanez writes:
"I send you the diagram below that reconciles quantum mechanics (diagram for filling the electronic cells) with the Janet table or LSPT. Explaining the duplication of periods with the duplication of the quantum number n, and the introduction of Tao (T) spin of the level or spin of the period, which explains the parity of the symmetric periods."
Published by Paneth in 1942 in an article in Nature in which he suggests that newly discovered elements such as Z = 43 should be given names by their discoverers. The other highlighted elements (below) had also not yet been named.
Element 43 had been discovered 9 years earlier but had not been given an official name because there was reluctance to consider synthetic elements on the same footing as naturally occurring ones. This changed as a result of Paneth's article.
The Periodic Law, one of the great discoveries in human history, is magnificent in the art of chemistry. Different arrangements of chemical elements in differently shaped Periodic Tables serve for different purposes. "Can this Periodic Table be derived from quantum chemistry or physics?" can only be answered positively, if the internal structure of the Periodic Table is explicitly connected to facts and data from chemistry.
Quantum chemical rationalization of such a Periodic Tables is achieved by explaining the details of energies and radii of atomic core and valence orbitals in the leading electron configurations of chemically bonded atoms. The coarse horizontal pseudo-periodicity in seven rows of 2, 8, 8, 18, 18, 32, 32 members is triggered by the low energy of and large gap above the 1s and nsp valence shells (2 ≤ n ≤ 6 !). The pseudo-periodicity, in particular the wavy variation of the elemental properties in the four longer rows, is due to the different behaviors of the s and p vs. d and f pairs of atomic valence shells along the ordered array of elements. The so-called secondary or vertical periodicity is related to pseudo-periodic changes of the atomic core shells.
The Periodic Law of the naturally given System of Elements describes the trends of the many chemical properties displayed inside the Chemical Periodic Tables. While the general physical laws of quantum mechanics form a simple network, their application to the unlimited field of chemical materials under ambient 'human' conditions results in a complex and somewhat accidental structure inside the Table that fits to some more or less symmetric outer shape. Periodic Tables designed after some creative concept for the overall appearance are of interest in non-chemical fields of wisdom and art.
An interactive, searchable Google map of places associated with the developers of the periodic table and with the chemical elements with links to further information brought to you by Carmen Giunta and James Marshall, with the encouragement of the ACS Division of the History of Chemistry (HIST), to mark the International Year of the Periodic Table (IYPT).
This is an interactive searchable map of places associated with the developers of the periodic table and with the chemical elements with links to further information.
Examples include places where elements were discovered or synthesized, mineral sources of elements, places where discoverers of chemical periodicity worked, and places for which elements were named. Each entry contains links to further information about the person, place, or event described. The type of site is indicated (for example, lab, residence, mineral source, etc.), as well as whether (to the best of our knowledge) the historical site still exists at the location. For more information on the type of site, please consult this key to the map's fields. The map is intended for educational and informational purposes only, and is not meant as a travel guide. If you wish to visit a site on this map, please consult other resources to confirm access, and use common sense. (Read more here.)
From the RSC Website: "Alchemists are often described as the first chemists. They developed an extraordinary language (rather than the chemical symbols we use today) to describe all manner of things, from chemical reactions to philosophical tenets. Click on ‘What is Alchemy?’ to learn about the three aims of the alchemists. Click on each of the alchemical symbols for more information and to see alternative symbols."
IUPAC Periodic Table Quantum Mechanics Consistent, Bernard Schaeffer, Journal of Modern Physics, Vol. 5, No. 3, February 24, 2014 DOI: 10.4236/jmp.2014.53020
Abstract: Most periodic tables of the chemical elements are between 96% and 100% in accord with quantum mechanics.
Three elements only do not fit correctly into the official tables, in disagreement with the spherical harmonics and
the Pauli exclusion principle. Helium, belonging to the s-block, should be placed beside hydrogen in the s-block
instead of the p-block. Lutetium and lawrencium belonging to the d-block of the transition metals should not be
in the f-block of the lanthanides or the actinoids. With these slight modifications, the IUPAC table becomes
quantum mechanics consistent.
Students are expected to know that in all equations hydrogen is molecular should [nearly always] be written as H2. Likewise, nitrogen is N2, oxygen O2, fluorine F2, chlorine Cl2, bromine Br2 and iodine I2. But somehow students are expected to know that molecular sulfur, S8, should be written as S and molecular phosphorus, P4, should be written as P.
Extended Average Level (EAL) Dirac–Fock calculations on atoms and ions agree with earlier work in that a rough shell-filling order for the elements.
[This new] Periodic Table develops further that of Fricke, Greiner and Waber [Theor. Chim. Acta 1971, 21, 235] by formally assigning the elements 121–164 to (nlj) slots on the basis of the electron configurations of their ions. Simple estimates are made for likely maximum oxidation states, i, of these elements M in their MXi compounds:
Scientists from Moscow Institute of Physics and Technology and Skoltech have demonstrated the high-temperature superconductivity of actinium hydrides and discovered a general principle for calculating the superconductivity of hydrides based on the periodic table alone. The results of their study were published in The Journal of Physical Chemistry Letters.
Too much sugar can be detrimental to health, rotting teeth, building fat, damaging blood vessels and stressing out the system that regulates blood sugar. Some people turn to artificial sweeteners, but those are under increasing suspicion of creating metabolic problems, such as diabetes and obesity.
Natural alternative sweeteners exist, but even they have pitfalls if consumed in excess.
This sweetners periodic table below, click to enbiggen, charts the wide variety of sweeteners available in the United States, either in bulk amounts or as additives in food.
Not listed are super-sweet-tasting, zero-calorie proteins from several African fruits (monellin, brazzein and thaumatin), which have not been approved for use by the FDA. Also not included: banned or poisonous sweeteners, such as lead acetate, which ancient Romans made by cooking sour wine in lead pots.
In quantum mechanics, the term symbol is an abbreviated description of the (total) angular momentum quantum numbers in a multi-electron atom. Each energy level of an atom with a given electron configuration is described by not only the electron configuration but also its own term symbol, as the energy level also depends on the total angular momentum including spin. The usual atomic term symbols assume LS coupling (also known as Russell-Saunders coupling or spin-orbit coupling). The ground state term symbol is predicted by Hund's rules.
Neutral atoms of the chemical elements have the same term symbol for each column in the s-block and p-block elements, but may differ in d-block and f-block elements, if the ground state electron configuration changes within a column.
By Steven Murov, a chronology of the events that have resulted in our present periodic table of the elements and
a celebration of the 150th anniversary of the Mendeleev (birthday, 02/08/1834) periodic table (1869).
"I will be delighted if I could have a chance to contribute for the fantastic moment expressed by 2019 IYPT.
"I am senior Professor of Chemistry at the University of São Paulo, and great Periodic Table enthusiast since the beginning of my career about 50 years ago. This interest actually came from my supervisor and mentor, Professor Henry Taube (Nobel Prize, 1983), who taught me the beauty of the elements."
"As an inorganic chemist, I have been collecting the elements and minerals for a long time, and I built up the Periodic Table with the real elements shown below. It is one of the attractions of the campus, and has been reported in many publications1. It was visited by colleagues from IUPAC, including the President. I wouldn't be surprised if it inspired IUPAC the similar Table exposed in Paris, this year. The difference is that our table is that it also places the typical minerals together with the elements, and I believe that this is very important aspect for teaching and discussing the history behind them:
"Next, is my personal version of the IUPAC Periodic Table, shown in Figure 2, with the isotopes distributed in a column right to the element symbol. This Table is very practical, and particularly useful when you are dealing with mass spectrometry or isotopes. It is in my book of Elements2.
"Another is the Periodic Table of the Elements for Life, with the essential elements and abundance expressed by colors, including those used in medicine. This Table will be changing with the progress of Bioinorganic Chemistry, and is in my book of Bioinorganic Chemistry3.
"Finally, I have adapted the periodic table of elemental sustainability, using the colors to call attention for this issue. In this form, it is can be more easily understood by the public. Elemental Sustainability is a very important issue, as discussed in Green Chemistry Journal4.
Toma, H. E. IYPT 2019 International Year of the Periodic Table of the Chemical Elements. Quimica Nova42, 468–472 (2019).
Toma, H. Estrutura atômica, ligações e estereoquímica. (Edgard Blucher, 2018).
Toma, H. Química bioinorganica e ambiental. (Edgard Blucher, 2015).
Toma, H. Green Processing of Strategic Elements Based on Magnetic Nanohydrometallurgy. Green Chem. 29, 948–959 (2015).
While the 'ultimate' periodic table by Goodfellowmay not appear to be very ultimate, it does actually a possess a very rare property: Goodfellow is a materials company that supplies most of the chemical elements for industrial and research use.
By clicking on the element palladium, various facts about, and properties of, Pd are shown. Additionally, Goodfellow can supply:
Upper Limit in Mendeleev's Periodic Table - Element No.155
This book (PDF), by Albert Khazan, represents a result of many-year theoretical research, which manifested hyperbolic law in Mendeleev's Periodic Table.
According to [Khazan's] law, an upper limit (heaviest element) exists in Mendeleev's Table, whose atomic mass is 411.66 and No.155. It is shown that the heaviest element No.155 can be a reference point in nuclear reactions. Due to symmetry of the hyperbolic law, the necessity of the Table of Anti-Elements, consisting of anti-substance, has been predicted. This manifests that the found hyperbolic law is universal, and the Periodic Table is common for elements and anti-elements.
To celebrate the International Year of Chemistry (IYC), Chem 13 News magazine together with the University of Waterloo's Department of Chemistry and the Faculty of Science encouraged chemistry educators and enthusiasts worldwide to adopt an element and artistically interpret that element.
The project created a periodic table as a mosaic of science and art. Students from all Canadian provinces and territories, 20 U.S. states and 14 countries researched, created and designed the elemental tiles. We created a poster, wall mural and a mobile app. The app includes the creative process behind each tile along with basic atomic properties of the element. The free app work to truly highlight the artistic expression of the Periodic Table Project. Thank you to all the teachers and students who participated in the collaborative Periodic Table Project.
Mark Winter's WebElements was started in 1993 when it was one of the first websites on the internet.
Mark Leach's Chemogenesis web
book uses the WebElements periodic table as its master data source, and
it does not attempt to duplicate it.
elements (Earth's crust)
Abundance of elements (oceans)
Abundance of elements (sun)
Abundance of elements (Universe)
Abundance of elements (in human body)
Accurate mass of the isotopes
Block in periodic table
Bond enthalpy (diatomics)
Bond length in element
Element bond length
Enthalpy of atomization
Enthalpy of fusion
Enthalpy of vaporization
Examples of compounds
Group name numbers
History of the element
Meaning of name
Names and symbols
Origin of name
Period in table
Properties of some compounds
Radius (van der Waals)
Radius metallic (12)
Standard atomic weights
Structure of element
Van der Waals radius
X-ray crystal structure
The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe.
The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen.
Much of the iron in your body was made during supernovas of stars that occurred long ago and far away.
The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts.
Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life.
The featured periodic table, from Astronomy Picture of The Day (APOD) is color coded to indicate humanity's best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.
It is apparent that chemistry the years 1810 to 1850 was largely concerned with discovering the whole number stoichiometric ratios of atoms in chemical compounds.
Wollaston writes in the text above:
"It is impossible in several instances, where only two combinations of the same ingredients are known, to discover which of the compounds is to be regarded as consisting of a pair of single atoms, and since the decision of these questions is purely theoretical, and by no means necessary to the formation of a table adapted to most practical purposes, I have not been desirous of warping my numbers according to an atomic theory, but have endeavored to make practical convenience my sole guide, and have considered the doctrine of simple multiples, on which that of atoms is founded, merely as a valuable assistant in determining, by simple division, the amount of those quantities that are liable to such definite deviations from the original law of Richter."
"Mr. Dalton in his atomic views of chemical combination appears not to have taken much pains to ascertain the actual prevalence of that law of multiple proportions by which the atomic theory is best supported [however] it is in fact to Mr. Dalton that we are indebted for the first correct observation of such an instance of a simple multiple in the union of nitrous gas with oxygen."
"[I have] computed a series of supposed atoms, I [have] assumed oxygen as the decimal unit of my scale [ie. oxygen = 10], in order to facilitate the estimation of those numerous combinations which it forms with other bodies. Though the present table of Equivalents, I have taken care to make oxygen equally prominent on account of the important part it performs in determining the affinities of bodies by the different proportions in which it is united to them.."
Mark Leach writes:
"When Wollaston's equivalent weights are converted from O = 10.00 to the modern value of O = 15.999, the atomic weight values can be seen to be astonishingly accurate.
"However, the language of the article is quite difficult as the meaning of many of the terms is unclear (to me, at least). For example, in modern usage adding 'ia' to a metal implies the oxide: 'magnesia' is magnesium oxide, MgO. I am not clear if this historical usage is consistent. 'Azote' is nitrogen and 'muriatic acid (dry)' is hydrogen chloride gas. I have only analyses/re-calculated the elements and a couple of common/obvious compounds:"
Scaled to O = 15.999
H (as H2)
N (as N2)
Cl (as Cl2)
The elements hydrogen, nitrogen (azote) and chlorine have clearly been measured as the diatomic molecules, even if this was unknown to Wollaston in 1813.
Phosphorus is out by 11%... [fair enough].
Only silver is clearly wrong, but it is out by 50% so it looks like a simple stoichiometry error: Perhaps the oxide was assumed to be AgO was instead of the correct Ag2O.