Lithium (symbol Li)
has one electron outside the two-electron "helium core" and three
protons in its nucleus, giving an electronic arrangement that can
be represented by Li 2,1. In the electronic structure diagrams
spanning pages 2 to 5,
including the figure above, Li has one electron in the white
region that represents the incomplete second shell. The man who
invented the idea of electron-pair bonds, University of California
chemist G. N. Lewis, represented the outer-shell electrons of atoms
as dots around the atomic symbol, as shown at the bottom right of
Lithium is a soft, silvery metal
that enters into chemical reactions with other substances extremely
readily, losing its outer electron in the process.
Beryllium (Be) has two electrons in its second shell,
and is symbolized by Be 2,2 or by the Lewis dot structure
on page 7. It is a harder and less reactive
metal than lithium.
Boron, (B) with three outer electrons (B 2,3),
is gray, brittle, and only slightly metallic.