"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."