All s-block elements predominately form ionic compounds.
Ionic bonding is a type of chemical bond in which valence electrons are lost from one atom and gained by another. Ionic bonds involve a cation and an anion.
So, elements that easily lose or gain electrons will readily form ionic compounds.
If we analyse s-block elements they can easily form cations because they have:
a. large size
b. low ionization enthalpy
c. low electron affinity
We can draw a conclusion that all s-block elements predominantly form ionic compounds.
But this statement is not completely true.
Li and Be do not readily form ionic compounds even though they are s-block elements. The reason being Li and Be have high ionisation enthalpy in the group, so the tendency to form cation is less.
As a result and the tendency to form ionic compounds is low and these elements are more prone to form covalent bonds.