What is the formula for barium hydroxide?
Barium is an element in Group 2, so it has two valence electrons, and that it's charge is 2+.
Hydroxide is a polyatomic negative ion with a valency of 1, and that it's charge is 1-.
As barium is a metal while hydroxide is a non-metal, they combine to form an ionic compound.
To form a neutral compound, balance the positive and negative charges by applying LCM,and the number of positive and negative charges must be equal.
As seen from above, one barium ion and two hydroxide ions form barium hydroxide. Thus, the formula of barium hydroxide is