The radius of a lithium atom is 130 picometers, and the radius of a fluorine atom is 60 picometers. the radius of a lithium ion, li⁺, is 59 picometers, and the radius of a fluoride ion, f⁻, is 133 picometers. explain, in terms of subatomic particles, why the radius of a lithium ion is smaller than the radius of a lithium atom.

A positive ions is always smaller than the corresponding atom.

A negative ion is always larger than the corresponding atom.

Explanation:

The reason for this is that, when a positive ion is formed, a full shell is usually removed with its electrons thereby reducing the size of the electron cloud and decreasing the size of the electron cloud.

A negative ion is formed by addition of more electrons to the electron cloud hence it spreads out. Interelectronic repulsion accounts for the larger size of the negative ion.