Question

Define the ‘Mass defect’ of a nucleus.

Answer 1

The mass defect of a nucleus is the difference between the mass of the completely assembled nucleus and the sum of the masses of the individual protons and neutrons that make it up.

Δ_m = `(Zm_p + Nm_n) - M_"nucleus"`

Where, 

Z = Number of protons,

N = Number of neutrons,

m_p = Mass of a proton,

m_n = Mass of a neutron,

`M_"nucleus"` = Actual mass of the nucleus