Question

What is atomic number and what is mass number ?

Answer 1

one is the average weight of an element and the other is the total number of nucleons in the atom's nucleus.

Answer 2

atomic number
the number of protons in one atom of an element is known as atomic number of that element.

atomic number of and element = number of protons in one atom of element .

mass number
the total number of protons and neutrons present in one atom of an element is known as its mass number .

mass number = number of protons + number of neutrons .