Elements react with other elements because
they are energetically
unstable.
Atoms of noble gases are energetically
stable while the rest of the elements in the periodic table are
not.
–Atoms of noble gases are energetically
stable because their valence shells contain the maximum number of electrons
that they can accommodate.
So, atoms of other elements try to
attain a similar electronic structure as those of noble gases and they do so by
reacting with other elements.
In order to achieve the same electronic
structure as a noble gas, group 1 metals have two options
–gain 7 electrons and become like the noble
gas in their own period, or
–lose 1 electron and become like the noble
gas in the period above them.