Question

What is the difference between the ionic radius and the atomic radius of an element?

Answer 1

The ionic radius is the the distance from the nucleus to the outermost electrons in a ion.

While the atomic radius is the distance from the nucleus to the normal valance electrons.

Explanation:

The ionic radius in a positive ion is less than the distance from the nucleus to the valence electrons.

The ionic radius in a negative ion is greater than the distance from the nucleus to the valence electrons.

Losing electrons reduces the electron orbitals making the radius smaller.

Gaining electrons increases the electron orbitals making the radius larger.

You can see these trends in the image below.