The
alkali metals, in Group IA at the left of the table, all have a
single electron outside of a filled noble-gas shell. They have low
ionization energies, and hence a strong tendency to lose the outer
electron and become oxidized to the +1 state. This tendency is so
strong (it is stronger for the larger atoms at the bottom of the
group) that the alkali metals always occur in nature as +1 ions,
never as pure metals. They are found in sea water and brine wells,
in deposits of soluble salts such as NaCl and
and as cations in many less soluble or insoluble minerals such as
the silicates.
and make up
a little over 3% of the atoms in the crust of the Earth. The heavier
alkali metals rubidium and cesium are rarer, but are found in small
amounts in KCI and NaCl deposits.