Answer: Option (a) is the correct answer.
Explanation:
In order to gain electrons to attain stability, the valence shell should be smaller because smaller is the valence shell more closer it will be to the nucleus of the atoms.
Hence, more closer is shell to the nucleus more easily it can pull the electrons towards itself.
Thus, we can conclude that the electron shell should be small so that electrons are more easily gained best describes the electron shell in which the valence electrons are located.
