Question

After emission of an plane particle from ${}_{92}{U}^{238}$ nucleus, the number of neutrons in the new nucleus are:

• A. $144$
• B. $138$
• C. $90$
• D. $134$

Answer 1

The correct option is A $144$

After emission of an $\alpha$ particle the atomic number of new nuclei will be $Z=92-2=90$ and mass number will be $A=238-4=234$

so neutrons in the new nucleus will be $A-Z=234-90=144$