NTSE Stage 2 SAT 2019 Exam Question Paper

Question : 76 of 100

Marks: +1, -0

Manya,Kartik, Gurnoor and Sheena had arranged the ions

F^{-},Na^{+},O^{2-}

and

Mg^{2+}

Manya -

O^{2-} > Mg^{2+} > F^{-} > Na^{+}

Kartik -

Mg^{2+} > Na^{+} > O^{2-} > F^{-}

Gurnoor -

O^{2-} > F^{-} > Na^{+} > Mg^{2+}

Sheena -

F^{-} > Na^{+} > O^{2-} > Mg^{2+}

Who had provided the correct order of their decreasing ionic radii?

Manya
Kartik
Gumoor
Sheena

Validate

Solution:

The ions

F^{-},Na^{+},O^{2-}

and

Mg^{2+}

are isoelectric species having same electronic configuration but their nuclear charges differ from each other because of their difference in the number of protons in the nucleus. With increase in the number of protons in the nucleus, the electrons are more attracted towards nucleus thereby causing the decrease in ionic radius.Therefore, the given ions are

F^{-}

: no.of protons = 9 and no. of electron = 10

Na^{+}

:no.of protons = 11 and no. of electron =10

O^{2-}

::no.of protons = 8 and no. of electron =10

Mg^{2+}

:no.of protons = 12 and no. of electron =10

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