Carbon (C 2,4) and
the elements that follow all are nonmetals. Pure carbon occurs both
as the slightly metallic black graphite, and the clear and extremely
hard nonmetallic diamond. But carbon is much more familiar in the
myriad compounds that it forms with other elements. Carbon compounds
are the basis of all life. We cannot open our eyes on this planet
without seeing carbon compounds, from the most distant treeline
to the tip of our own nose.
Nitrogen (N 2,5) has five outer electrons. It combines
with carbon to form compounds in
living organisms. Nitrogen is found as two-atom or diatomic molecules,
molecules of hydrogen).
gas makes up nearly 80% of the Earth's atmosphere. The electron-shell
diagram for nitrogen above, and the Lewis dot structure on page
7, both suggest that two of the five outer electrons are paired
in some way. This is true. The pairing of electrons around an atom
is as important in determining its chemical properties as is the
pairing of electrons in a bond between atoms.