Chemistry Author

The number of protons in a nucleus is called the atomic number. The elements are arranged on the table in order of increasing number of protons in the nucleus.

Atomic Mass Atomic mass is the total mass of the subatomic particles in an atom and is measured in atomic mass units (amu). Atomic mass can be found by adding up the total masses of subatomic particles in an atom. Because both protons and neutrons have an atomic mass of 1 amu, and electrons have masses of such little consequence, atomic mass can be calculated by adding up the total number of protons and neutrons in an atom. Additionally, atomic mass can be found on the period table of elements. Why Atomic Masses are not always whole numbers? (Video Explanation)