Answer: The alkali metal atom forms a +1 ion, while the alkaline earth metal atom forms a +2 ion.
Explanation: Group 1 elements are called as alkali metals and group 2 elements are called as alkaline earth metals.
For example, Li is an alkali metal and Be is an alkaline earth metal.
Lithium(Li) has an atomic number of 3 and the electronic configuration is:
Li:

Thus lithium has to lose 1 electron and acquire 1+ charge to attain nearest noble gas configuration.

Berrylium(Be) has an atomic number of 4 and the electronic configuration is:
Be:

Thus berrylium has to lose 2 electrons and acquire 2+ charge to attain nearest noble gas configuration.
