Respuesta :

By the difference between the mass of an isotope and its mass number.

Answer: The equation for the mass defect is given below.

Explanation:

Proton and neutron, both combine to form a nucleus but the mass of a nucleus is found to differ from the actual sum of masses of proton and neutrons. This difference in the mass is called as mass defect.

This is given by the equation:

[tex]\Delta m=Xm_p+Ym_n-M[/tex]

where,

[tex]\Delta m[/tex] = Mass defect

X = Number of protons = Atomic number

[tex]m_p[/tex] = Mass of one proton

Y = Number of neutrons = (Atomic mass - Atomic number)

[tex]m_n[/tex] = Mass of one neutron

M = Mass of an atom