Question

among Na, Mg, Al and Si, which has smallest radius​

Answer 1

Answer:

The smallest radius is of Si ( Silicon ).

Explanation:

All the elements are from 3rd period, meaning all of them have 3 shells. But silicon has maximum no. of electrons in its outer shell, and hence the electromagnetic forces between the protons in nucleus and electrons in outer shell is more, because of which the radius gets contracted.

Bonus:

In a period the radius of atoms decreases as we move towards right. However, the last group elements that is the noble gases have a slightly larger radius than the previous elements. This is because they already have 8 electrons in their valence shell, hence to prevent repulsion the electrons tend to be away from each other.