On Food and Cooking

roughly similar affinities for electrons, they
will share them rather than gain or lose them
entirely. In order for sharing to occur, the
electron clouds of two atoms must overlap,
and this condition results in a fixed
arrangement in space between two particular
atoms, which thus form a stable combined
structure. The bonding geometry determines
the overall shape of the molecule, and
molecular shape in turn defines the ways in
which one molecule can react with others.
The elements most important to life on
earth — hydrogen, oxygen, carbon, nitrogen,
phosphorus, sulfur — all tend to form
covalent bonds, and these make possible the
complex, stable assemblages that constitute
our bodies and our foods. The most familiar
pure chemical compounds in the kitchen are
water, a covalent combination of two
hydrogen atoms and an oxygen; and sucrose,
or table sugar, a combination of carbon,
oxygen, and hydrogen atoms. Covalent bonds