Identify what is required to calculate the atomic number and atomic mass of an element

To identify the atomic number of any element, we need to know the numbers of electrons or protons in that particular element, because number of electrons always = number of protons and this is equals to atomic number.

To calculate the atomic mass of an element, we need to know the mass of protons and neutrons in the nucleus of an element. The sum of the protons, and neutrons is equals to atomic mass