Linus Pauling: Langmuir in 1881 to 1957. In 1919 he had two or three papers in the Journal of the American Chemical Society and a couple of notes in Science in 1920 and he gave many lectures. These were long papers, with a much more detailed
discussion of individual substances than in G.N.'s 1916 paper. Lewis...Langmuir, introduced
something into chemistry -- the word covalent.
This was the first time that anyone had spoken of covalence and covalent bonds. He
introduced the idea of formal charge saying you can split the electron pair, that
is the chemical bond, between the two atoms and then count up how many electrons there
are on each atom and what its resultant charge would be, an important idea. He was
really very clever. He said nitrous oxide is not a ring, the way some people had written
it, it isn't N-O-N with oxygen in the middle, it's N-N-O with an oxygen on one end,
a nitrogen atom in the middle, a nitrogen atom on the other end, formal charge -1
for the end nitrogen, +1 for the middle nitrogen, and zero for oxygen. He introduced
the principle of electroneutrality, that the charges on the atoms need to be 0 or
+1 or -1, that is almost zero. That is, you can take an electron off of an atom. The
first ionization energy for some atoms isn't awfully, some metals isn't very great,
you can take an electron off. Takes much more energy to pull a second electron off
so it's unlikely that that would be the situation in a stable molecule or crystal.
This was a very valuable principle overlooked. He had an idea that nickel tetracarbonyl
is octavalent, that the nickel atom forms four double bonds with oxygen and this was
required, rather than G.N. Lewis's structure with single bonds around the nickel atom,
by his electroneutrality idea.