Answer is: the amu of a sodium atom is 23.
The unified atomic mass unit (amu) is a standard unit of atom mass.
One unified atomic mass unit is approximately the mass of one nucleon (proton or neutron).
The unified atomic mass unit is equal 1.66·10⁻²⁷ kg.
n(p⁺) = 11; number of protons in sodium atom.
n(n°) = 12; number of neutrons of sodium atom.
n(p⁺ + n°) = 11 + 12.
n(p⁺ + n°) = 23; number of nucleons in sodium atom.
