Question

$ Li $ nucleus has three protons and four neutrons. Mass of lithium nucleus is $ 7.016005 $ amu. Mass of proton is $ 1.007277 $ amu and mass of neutron is $ 1.008665 $ amu. Mass defect for lithium nucleus in amu is:

• A. 0.04048 amu
• B. 0.04050 amu
• C. 0.04052 amu
• D. 0.04055 amu
• E. 0.04058 amu

Answer 1

Answer: (B)

Mass defect = mass of nucleons - mass of nucleus
$ =(3\times 1.007277+4\times 1.008665)-7.016005 $
$ =0.040486\text{ }amu $
$ \approx 0.04050\text{ }amu $