How can there be more than 1000 different atoms when there are only about 100 different elements?

When water dissociates, each water molecule splits into a hydroxide ion and a) h 3 o + b) a hydrogen atom c) a hydrogen ion d) h 2 o e) oh —

Elements in group 2 are all called alkaline earth metals. what is most similar about the alkaline earth metals?

If 2 molecules of one reactant combine with 3 molecules of another to produce 5 molecules of a product, then what is the representation of the reaction?