Question

The mass of helium atom of mass number $4$ is $4.0026$ amu, while that of the neutron and proton are $1.0087$ and $1.0078$ respectively on the same scale. Hence, the nuclear binding energy per nucleon in the helium atom is nearly

• A. 5 MeV
• B. 7 MeV
• C. 10 MeV
• D. 14 MeV

Answer 1

Answer: (B)

He atom has $2p+2n$
Hence,
$\Delta m=(2\times 1.0078+2\times 1.0087)-4.0026$
$=0.0304\,amu$
$\therefore$ energy released
$=0.0304\times 931.5\,MeV$
$=28.3\,MeV$
Binding energy per nucleon
$=\frac{28.3}{4}=7\,MeV$ (approximately)