JEE Main · 2007 · 29 Apr 2007 · Offline · Chemical Bonding and Molecular Structure

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The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizinig order of the polarizing power of the cationic species,

K^{+}, Ca^{2 +}, Mg^{2 +}, Be^{2 +}

(A) $Mg^{2 +}, Be^{2 +}, K^{+}, Ca^{2 +}$
(B) $Be^{2 +}, K^{+}, Ca^{2 +}, Mg^{2 +}$
(C) $K^{+}, Ca^{2 +}, Mg^{2 +}, Be^{2 +}$ ✓ Correct
(D) $Ca^{2 +}, Mg^{2 +}, Be^{2 +}, K^{+}$

Answer: (C)

Solution

Polarising power rises with the charge-to-size ratio, so a small, highly charged cation polarises most strongly. Among these, the singly charged

K^{+}

is large and weakest; the doubly charged ions increase in power as their size shrinks, from

C a^{2 +}

M g^{2 +}

to the very small

B e^{2 +}

. The increasing order is therefore

K^{+} < C a^{2 +} < M g^{2 +} < B e^{2 +}

JEE Main · 2007 · 29 Apr 2007 · Offline · Single correct option

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JEE Main · 2007 · 29 Apr 2007 · Offline · Chemical Bonding and Molecular Structure

Solution

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