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JEE Main levelSingle correct optionDifficulty 2 of 3pt016

The ion is isoelectronic with argon. The element M lies in

  1. Agroup 3, period 4
  2. Bgroup 13, period 3
  3. Cgroup 15, period 3
  4. Dgroup 3, period 3

Answer: A

Ar has 18 electrons, so M has electrons (Z = 21, scandium) with configuration . This is group 3, period 4. is isoelectronic with neon, not argon.
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