Question

Describe the theory associated with the radius of an atom. As it gains an electron

Answer 1

Answer:

It considers that the electrons are attracted to the nucleus and are also repelled by each other.

An outer electron is "shielded" from the attraction of the nucleus by the inner electrons and a bit by the other outer electrons.

The greater the shielding, the less the attraction experienced by the outermost electrons.

Gaining an electron

Consider a fluorine gaining an electron to form a fluoride ion.

A fluorine atom has nine electrons and nine protons.

An outer electron is partially screened by the other eight electrons.

It "sees" only an effective charge of +5.2, and this determines its atomic radius.

If we add a tenth electron, it is now partially screened by the other nine electrons.

It sees an effective charge of +4.85.

The attraction for the nucleus is less, so the electrons spend more of their time further from the nucleus.

The atomic radius increases.