Anybody know a little chemistry? Zinc Sulfate monohydrate vs heptahydrate.

Ok first question. When people talk about zinc as a supplement. What is the difference how can you have 15 forms of zinc (or any other mineral for that matter) piconate, sulfate, chelate, glycate etc. What is the difference? Why so many why not just ZINC? In addition I am trying to make a solution of 1% zinc sulfate to make a zinc taste test. I have 220mg zinc sulfate equivelent to heptahydrate. My instructions say to mix 2000 mgs of zinc sulfate with 2 liters, which is a 1% solution of zinc sulfate. So approx 9 capsules of 220 mg will be about 2000 mgs. The back of the bottle says Zinc Sulfate Monohydrate equavilent to 220 mg zinc heptahydrate. 50 mg is the actual supplementation. What the heck is the difference between Zinc Sulfate Heptahydrate and monohydrate. I know that one is a compound of H20 and a the other 7 compounds of H20.

Thanks