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NEET 2015
Exam
NEET
Year
2015
Subject
Chemistry
Chapter
Classification of Elements and Periodicity in Properties

NEET 2015 · Chemistry · Classification of Elements and Periodicity in Properties

The species Ar, K ^ + and C a ^ 2 + contain the same number of...

The species Ar,K+Ar, {K}^{+} and Ca2+C{a}^{2 +} contain the same number of electrons. In which order do their radii increase?

Options

  1. AAr<K+<Ca2+Ar < {K}^{+} < C{a}^{2 +}
  2. BCa2+<Ar<K+C{a}^{2 +} < Ar < {K}^{+}
  3. CCa2+<K+<ArC{a}^{2 +} < {K}^{+} < Ar
  4. DK+<Ar<Ca2+{K}^{+} < Ar < C{a}^{2 +}

Correct answer

C. Ca2+<K+<ArC{a}^{2 +} < {K}^{+} < Ar

Step-by-step solution

For isoelectronic species as ze\dfrac{z}{e} ratio increases ionic size decreases.

(Total no. of electrons) = 18

For Ar(ze)=1818Ar\left(\dfrac{z}{e}\right) = \dfrac{18}{18}

K+(ze)=1918{K}^{+}\left(\dfrac{z}{e}\right) = \dfrac{19}{18}

Ca2+(ze)=2018C{a}^{2 +}\left(\dfrac{z}{e}\right) = \dfrac{20}{18}

i.e. Ca2+<K+<ArC{a}^{2 +} < {K}^{+} < Ar
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