Question

Calculate the mass defect when three $\alpha$-particle combine to form a ${}^{12}C$ nucleus :
(Atomic mass of ${}_2{He}^4$ is $4.002603u$)

• A. $0.007809u$
• B. $0.002603u$
• C. $4.002603u$
• D. $0.5u$

Answer 1

The correct option is A $0.007809u$

Mass defect
$\Delta m=$ Total mass of $\alpha$-particles $-$ mass of ${}^{12}C$ nucleus
$=3\times 4.002603-12=12.007809-12$
$=0.007809$ unit