Verified Solution • 2025–26 Session moderate

QJEEM21Ch908d: JEE Main 2021 Chemistry - Class 11 JEEM21Ch908d Solution: The ionic radii of K + , Na + , Al 3+ and Mg 2+ are in the order:

The ionic radii of K+, Na+, Al3+ and Mg2+ are in the order:

Multiple Choice Options

  • A Na+ < K+ < Mg2+ < Al3+
  • B Al3+ < Mg2+ < K+ < Na+
  • C Al3+ < Mg2+ < Na+ < K+
  • D K+ < Al3+ < Mg2+ < Na+

Step-by-Step Verified Solution

Al3+, Mg2+ and Na+ are isoelectronic ionic species. For monoatomic ionic isoelectronic species as positive charge increases ionic size decreases.

The order of size of Na+ & K+ is Na+ < K+

∴ Order of ionic radii is : Al3+ < Mg2+ < Na+ < K+

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