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COMEDK2012ChemistryClassification of Elements and Periodicity in Properties

The atomic number of the element with highest ionisation energy among the following is

Options

  1. AZ=16
  2. BZ=14
  3. CZ=13
  4. DZ=15

Correct answer

D. Z=15

Step-by-step solution

The electronic configuration is (a) Z=16: 1 s² 2 s² 2 p⁶ 3 s² 3 p⁴ (b) Z=14: 1 s² 2 s² 2 p⁶ 3 s² 3 p² (c) Z=13: 1 s² 2 s² 2 p⁶ 3 s² 3 p¹ (d) Z=15: 1 s² 2 s² 2 p⁶ 3 s² 3 p³ For Z=15, p -orbital has stable half-filled configuration. It will have highest ionisation energy.

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