Question

When an atom undergoes $\beta$-decay, its atomic number

• A. Does not change
• B. Increases by $1$
• C. Decreases by $1$
• D. Increases by $2$

Answer 1

The correct option is B Increases by $1$

When an atom undergoes $\beta$-decay the atomic number increases by 1.

When an atom undergoes $\beta$-decay, one of the neutrons breaks into one proton and one electron. The resultant electron is then ejected out of the nucleus and this is called as the $\beta$ particle. While the resultant proton stays inside the nucleus which results in increase of atomic number by 1, whereas the atomic mass remains invariant.

Hence the correct answer is option B.