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JEE Main 202125 JulyMorning Shift
Exam
JEE Main
Year
2021
Date
25 July
Shift
Morning Shift
Subject
Chemistry
Chapter
Classification of Elements and Periodicity in Properties

JEE Main 2021 · 25 July · Morning Shift · Chemistry · Classification of Elements and Periodicity in Properties

The ionic radii of K ^ + , Na ^ + , Al ^ 3 + and Mg ^ 2 + are in...

The ionic radii of K+,Na+,Al3+{K}^{+}, {Na}^{+}, {Al}^{3 +} and Mg2+{Mg}^{2 +} are in the order :

Options

  1. ANa+<K+<Mg2+<Al3+{Na}^{+} < {K}^{+} < {Mg}^{2 +} < {Al}^{3 +}
  2. BAl3+<Mg2+<K+<Na+{Al}^{3 +} < {Mg}^{2 +} < {K}^{+} < {Na}^{+}
  3. CAl3+<Mg2+<Na+<K+{Al}^{3 +} < {Mg}^{2 +} < {Na}^{+} < {K}^{+}
  4. DK+<Al3+<Mg2+<Na+{K}^{+} < {Al}^{3 +} < {Mg}^{2 +} < {Na}^{+}

Correct answer

C. Al3+<Mg2+<Na+<K+{Al}^{3 +} < {Mg}^{2 +} < {Na}^{+} < {K}^{+}

Step-by-step solution

Al3+,Mg2+{Al}^{3 +}, {Mg}^{2 +} and Na+{Na}^{+} are isoelectronic ionic species. For monatomic ionic isoelectronic species as positive charge increases ionic size decreases.

The order of size of Na+ and K+{Na}^{+} \text{ and } {K}^{+} is Na+<K+{Na}^{+} < {K}^{+},

∴∴ Increasing order of ionic radii: Al3+<Mg2+<Na+<K+{Al}^{3 +} < {Mg}^{2 +} < {Na}^{+} < {K}^{+}

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