Question

What is the mass defect of Kr-84 in amu? Also, what is the Binding energy per nucleon (MeV/nucleon)?

Answer 1

Mass defect , ?m = ( ZM_H + (A-Z) M _n ) - M

Where

Z = atomic number = 36

(A-Z) = No. of neutrons = 84-36 = 48

M_H = mass of Hydrogen atom = 1.007825 amu

M _n = mass of Neutron = 1.008665 amu

M = real mass = 83.80 amu

Plug the values we get ?m = [( 36x1.007825)+ (48x1.008665 )] - 83.80

                                         = 0.89762 amu

So nuclear binding energy , BE = ?m x 931.5 MeV

                                              = 0.89762 x 931.5 MeV

                                               = 836.13303 MeV

                                               = 836.13303 x 10⁹ eV

                                               = 836.13303 x 10⁹ x 1.6x10^-19 J

                                               = 1.3378 x 10^-7 J

Binding energy per nucleon = BE / atomic mass number

                                        = 1.3378 x 10^-7 / 84 J / necleon

                                       = 1.59 x 10 ^-9 J/nucleon