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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.
Harrington's Crystal Chemistry of the Periodic System
R.H. Harrington, The Modern Metallurgy of Alloys, John Wiley & Sons, New York, p. 143 (1946)
René Vernon writes:
"The numbers below each element symbol refer to the crystal: 1 = FCC, 9 = graphite structure, 11 = orthorhombic, etc. Extra numbers are for structures at higher temperatures.
"The wriggly lines between groups 3 and 4, and 11 and 12 refer to a gradation between the classes involved. Wikipedia calls these linking or bridging groups
"Harrington's class names are novel. [Who would have thought of the elements of groups 1 to 3 as being called the "salts of electrons"?] Then again, "in view of the extensive role that electrons play as anions" Dye (2015) asked: "where should electrons be placed in the periodic table?" (Note: In 1946 Achimof tried answering this, with an electron as element -1 above H and a neutron as element 0 above He.)
"Aluminium appears in group 3 and group 13 since, according to Harrington, it has the crystalline structure of a true metal. This is not quite true since its crystalline structure shows some evidence of directional bonding.
"For the transition metals as "wandering bonds", Harrington writes that the metallic bond is spatially undirected and that it may operate between any given atom and an indefinite number of neighbours" (p. 145). Since A-metals are better called, in his mind, "salts of electrons" [and B-metals show signs of significant directional bonding] the transition metals are therefore called by him as wandering bonds. This becomes confusing, however, given d electrons in partially filed d-orbitals of transition metals form covalent bonds with one another.
"Counting boron as a pseudo metals looks strange.
"Germanium is counted as a metal: "...the electrical conductivit[y]... [is] sufficiently high to show that the outer electrons are very loosely held and the linkage must be partly metallic in character." (p. 148). In fact the electrical conductivity of high purity germanium, which is a semiconductor, is around 10–2S.cm–1. Compare this with antimony, at 3.1 x 104S.cm–1
"Tin has brackets around it to show its "renegade" status, "with its white form behaving largely as would a True Metal, whereas its grey form is more non-metallic than metallic." White tin actually has an irregularly coordinated structure associated with incompletely ionised atoms.
"Thallium and lead have brackets around them since their crystalline structures are supposedly like those of true metals. This is not quite right. While both metals have close-packed structures they each have abnormally large inter-atomic distances that have been attributed to partial ionisation of their atoms.
"The B-subgroup metals are divided into pseudo metals and hybrid metals. The pseudo metals (groups 11 and 12) behave more like true metals than non-metals. The hybrid metals As, Sb, Bi, Te, Po, At – which other authors would call metalloids – partake about equally the properties of both. According to Harrington, the pseudo metals can be considered related to the hybrid metals through the carbon column.
"The location of the dividing line between metals and nonmetals, running as it does through carbon to radon is peculiar. The line is usually shown running through boron to astatine."
"In 1863 Mr. John Newlands pointed out in a letter to the Chemical News that if the elements be arranged in the order of their atomic weights in a tabular form, they fall naturally into such groups that elements similar to each other in chemical behaviour occur in the same columns. This idea was elaborated farther in 1869 by Professor Mendeléeff of St. Petersburg and by the late Professor Lothar Meyer, and the table may be made to assume the subjoined form (the atomic weights are given with only approximate accuracy):—"
"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."
"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!"
Scerri's The Periodic Table: Its Story & Its Significance 2nd Edition
The 2nd Edition of Eric Scerri's well regarded book, The Periodic Table: Its Story & Its Significance has been published by Oxford University Press and is available at all good bookshops, including online.
A Novel Way of Visualization of the Periodic Table of the Elements by Alaa El-Deen Ali Mohamed, Alexandria University, Egypt.
The author writes:
"New form of the periodic table of the elements is given in this paper. This form can be seen as two amphitheater pyramids facing each other. The cubes that meet are s-elements (interior) then the p-elements then d-elements and the f-elements at last (exterior). The table can be represented by X-, Y- and Z-axes, where the Z-axis gives the number of the period that the element occupies. The table can be modeled by colored cubes helping in introducing the periodic table to the pupils early in the primary education."