In compound molecular mass is the sum of the individual atomic masses of the atoms.
For example
Compound NaCl.
atomic weight of sodium = 23 g/mol
atomic weight of chlorine = 35.5 g/mol
Molar mass of NaCl = 23+ 35.5 = 58.5 g/mol
Every atom consist of nucleus or a positive center. The protons and neutrons are present with in the nucleus while electrons are present out side the nucleus. All these three subatomic particles construct an atom. The number of protons or number of electrons are the atomic number of an atom while the number of protons and number of neutrons are the mass number of an atom. A neutral atom have equal number of protons and electrons. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other.
