What is the relationship between atomic number and atomic mass number?

= number of protons in nucleus of atom . Also called Proton number. number = number of protons and neutrons in the nucleus of atom . Also called Nucleus number.

First, lets define few terms:Proton - a particle hidden in nucleus of atom, carries 1 positive charge.Neutron - a particle hidden in nucleus of atom, carries no charge, is neutral.Electron - a particle found atomic capsule, surrounding the nucleus. Carries 1 negative charge.

Atomic number = number of protons in nucleus.Atomic = number of all particles in nucleus = protons + neutrons.

So, the answer is: Atomic number is a part of Atomic mass number.

THIS IS OPTIONAL

There is a similarly named term, called Atomic relative mass This explanation is in here if you intended to ask:"What is a relationship between atomic number and atomic relative mass?"

Atomic relative mass - is a constant. Its individual for each element in periodic system. Its basically "weight" of one atom. Because atom of each element contains different amount of particles, and these particles have certain mass, they have a weight as well.

Out of three particles (Protons, Neutrons, Electrons) Neutrons weight the most. m (proton) = ##1,67 × 10^(−27) kg## m (neutron) = ##1,7 × 10^(-27) kg## m (electron) = ##9,11 × 10^(-31) kg## Weight of electron is about 1800 times smaller then weight of Neutron... so it barely makes any difference.

This means that atomic relative mass is basically a sum of all weights of protons and neutrons (and electrons) in atom. This means that atomic relative mass depends on atomic number aka proton number (more precisely, it depends on the atomic relative mass, aka neutron number)