Question

What happens to the mass number of an element when an $\alpha$-particle, is emitted?

• A. It remains the same
  
• B. It decreases by $2$
  
• C. It decreases by $4$
  
• D. It increases by $2$
  

Answer 1

Answer: (C)

It decreases by $4$

As $\alpha$-particle has the mass number of $4$, the mass number of an element when an $\alpha$-particle, is emitted is decreased by $4$.