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Home » Consider the isoelectronic species, Na+, Mg2+, F–and O2–. The correct order of increasing length of their radii is _________.                
Consider the isoelectronic species, Na+, Mg2+, F–and O2–. The correct order of increasing length of their radii is _________.

    \[\left( \mathbf{i} \right)\text{ }{{\mathbf{F}}^{}}~<\text{ }{{\mathbf{O}}^{\mathbf{2}-}}~<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}\]


    \[\left( \mathbf{ii} \right)\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}<\text{ }{{\mathbf{F}}^{}}<\text{ }{{\mathbf{O}}^{\mathbf{2}-}}\]


    \[\left( \mathbf{iii} \right)\text{ }{{\mathbf{O}}^{\mathbf{2}-}}<\text{ }{{\mathbf{F}}^{}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}\]


    \[\left( \mathbf{iv} \right)\text{ }{{\mathbf{O}}^{\mathbf{2}-}}~<\text{ }{{\mathbf{F}}^{}}~<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}\]

CBSE | Chemistry | Class 11 | Classification of Elements and Periodicity in Properties | NCERT Exemplar
Consider the isoelectronic species, Na+, Mg2+, F–and O2–. The correct order of increasing length of their radii is _________.

    \[\left( \mathbf{i} \right)\text{ }{{\mathbf{F}}^{}}~<\text{ }{{\mathbf{O}}^{\mathbf{2}-}}~<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}\]


    \[\left( \mathbf{ii} \right)\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}<\text{ }{{\mathbf{F}}^{}}<\text{ }{{\mathbf{O}}^{\mathbf{2}-}}\]


    \[\left( \mathbf{iii} \right)\text{ }{{\mathbf{O}}^{\mathbf{2}-}}<\text{ }{{\mathbf{F}}^{}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}\]


    \[\left( \mathbf{iv} \right)\text{ }{{\mathbf{O}}^{\mathbf{2}-}}~<\text{ }{{\mathbf{F}}^{}}~<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}\]

Option (ii) is the answer.

Radius of elements increase as we move from left to right in a period. These are isoelectronic species having same number of electrons. As we move from left to right, from Magnesium to Oxygen, these belong to the same period and their radii goes on increasing. Hence , the sequence.

i

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