Chapter 8, Problem 8.48QP

Interpretation Introduction

Interpretation: Larger species among $H^{-}$ and $He$ has to be determined and explained.

Concept Introduction:

Ionic radius is the distance between the atomic nucleus and outermost shell having electrons of an ion. From the ionic radius, the size of ions can be visualized

When an atom gets converted to a cation, the charge of nucleus remains the same while the number of electrons decreases. This decreases the repulsion and hence the electron cloud reduces which results in the decrease in ionic radius.