• # question_answer Which one of the following is the smallest in size [IIT 1989] A) ${{N}^{3-}}$ B) ${{O}^{2-}}$ C) ${{F}^{-}}$ D) $N{{a}^{+}}$

$N{{a}^{+}}<{{F}^{-}}<{{O}^{2-}}<{{N}^{3-}}$ All are isoelectronic, effective number charge is highest for $N{{a}^{+}}$ so it has smallest size.