The atoms of a chemical element can exist in different types. These are called isotopes. They have the same number of protons (and electrons), but different numbers of neutrons.
The number of neutrons is variable, resulting in isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess. Together, the number of protons and the number of neutrons determine an element's mass number.
D.) It depends cuz no yeild is 100%..I mean side reactions also occur in most of the reactions. So mass of the reactant is not equal to the mass of the product. Hope it helps
