Group 1 metal compounds are
relatively stable—either they don’t decompose of if they do
decompose to fewer products—because of their strong reactivity.
In other words, the more
reactive the metal, the stronger the metal ion holds on to the
negative ion in the ionic lattice (stronger the bonds between
the positive metal ion and the negative ions).
Or state in another way, the
more reactive the metal, greater the tendency for the metal to
remain in the ionic form and therefore the more stable their
compounds.
This relative stability
extends to other ionic compounds as well, such as carbonates,
which when decompose, produce the oxide and carbon dioxide.