Definition of atomic mass unit

: a unit of mass for expressing masses of atoms, molecules, or nuclear particles equal to ¹/₁₂ the mass of a single atom of the most abundant carbon isotope Carbon-12.

Mass of electron = 5.5 x 10^-4u

Mass of proton = 1.00728 u

Mass of neutron = 1.00867 u

Binding Energy

Nuclear binding energy is the energy required to separate an atomic nucleus completely into its constituent protons and neutrons, or, equivalently, the energy that would be liberated by combining individual protons and neutrons into a single nucleus.

Mass Defect

The difference between an atom’s mass and the sum of the masses of its protons and neutrons.

E is the binding energy

m is the mass defect and needs to be in kg