Question

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

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

Answer 1

Answer: (A)

Here $m_p$ = 1.007277 amu,
$m_n$ = 1.008665 amu,
$m_{Li}$ = 7.016005 amu,
Sum of the masses of three protons and four neutrons = $3m_p+4m_n$
= 3 $\times$ 1.007277 + 4 $\times$ 1.008665
= 3.021831 + 4.03466
= 7.056491 amu
$\therefore$ Mass defect
= 7.056491 - 7.016005 = 0.040486 amu