Complete and balance the following reaction. Here we have solid strontium reacting with diatomic hydrogen gas. Strontium is in Group 2A so it's charges +2 or two. Plus, hydrogen here will have a charge and oxidation number of -1.

The numbers in the charges are different and when that happens they don't cancel out. The crisscross 2 comes here, one comes here at the end. That gives us SrH2 and this will be a solid.

Here our equation is already balanced because we have one strontium on each side and two hydrogens on each side. So this would be our final balanced chemical reaction.