Alkali metals are metals in Group I (far left column) such as Lithium, Sodium, Potassium, etc. They have a valence of -1.
Alkali Earth Metals are in Group II (second column from the left) such as Berylium, Magnesium, Calcium, etc. and have a valence of -2.
One Hydroxide (OH-) ion will form an ionic bond with group 1 elements {Like NaOH }, and two Hydroxide ions will form an ionic bond with group 2 elements {like Ca(OH)2 }
