Group displacement law states that the emission of alpha or beta particles results in the daughter element occupying a position

Explanation:

We know that,
Alpha emission decreases the atomic number by two. So, on the emission of α-particle daughter element shift 2 group to the left. Beta emission increases the atomic number by one.
So, on the emission of β-particle daughter element shift 1 group to the right.

Final Answer:

Hence, Option D is correct i.e, On emission of alpha particle - 2 groups to the left ; on emission of beta particle - 1 group to the right.