Question

Number of neutrons in a parent nucleus $X$, which gives ${}_7^{14}\text{N}$ after two successive $\beta$-emission would be :

• A. 6
• B. 7
• C. 8
• D. 9

Answer 1

The correct option is D 9

Reaction is:
${}_5^{14}\text{X}{⟶}_7^{14}\text{N}+2{}_{-1}^0\text{e}$
Number proton in X $=5$
Number of neutron$=14-5=9$