question_answer 51)

In the following Questions only one option is correct. Consider the isoelectronic species, \[N{{a}^{+}},M{{g}^{2+}},{{F}^{-}}\] and \[{{O}^{2-}}\]. The correct order of increasing length of their radii is : (a)\[{{F}^{-}}<{{O}^{2-}}<M{{g}^{2+}}<N{{a}^{+}}\]                                        (b) \[M{{g}^{2+}}<N{{a}^{+}}<{{F}^{-}}<{{O}^{2-}}\] (c) \[{{O}^{2-}}<{{F}^{-}}<N{{a}^{+}}<M{{g}^{2+}}\]                                        (d) \[{{O}^{2-}}<{{F}^{-}}<M{{g}^{2+}}<N{{a}^{+}}\]

Answer:

(b) In isoelectronic species, the ionic radii decrease as the nuclear charge increases, i.e., atomic number increases. \[M{{g}^{2+}}<N{{a}^{+}}<{{F}^{-}}<{{O}^{2-}}\]                            Z =12        11        9         8