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Formula Nucleus Mass number    Proton number    Neutron number

Formula
Formula: Nucleus
Nucleus and the Number of Protons and Neutrons

Mass number

Unit
Mass number is the number of nuclei, that is the sum of protons and neutrons in a nucleus. The mass number is different for different elements of the periodic table.

Proton number

Unit
Number of protons in a nucleus. The proton number is also called atomic number.

Neutron number

Unit
Number of neutrons in a nucleus.