Compare the radius of cation, anion and neutral atom.

Explanation

If the electron is added to neutral gaseous atom (anion), its size increases. As the electron is addedto valence shell, electron density increases. However, nuclear charge remains the same. As a result, electrons around nucleus expand and hence, size increases.

If electron is removed from neutral gaseous atom (cation), then electron density decreases and effective nuclear charge increases. Due to this, nucleus attracts remaining electrons with greater force and hence, size decreases. So, the order of radius of cation, anion and neutral atom is, Cation `lt` 0Neutral atom `lt` Anion