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NEET2005ChemistryClassification of Elements and Periodicity in PropertiesActual

Assertion : First ionization energy for nitrogen is lower than oxygen. Reason : Across a period effective nuclear charge decreases.

Options

  1. AIf both assertion and reason are true and reason is the correct explanation of assertion
  2. BIf both assertion and reason are true but reason is not the correct explanation of assertion
  3. CIf assertion is true but reason is false
  4. DIf both assertion and reason are false.

Correct answer

D. If both assertion and reason are false.

Step-by-step solution

First ionization energy for nitrogen is greater than oxygen. array ccc & N & O eV & 14.5 & 13.6 array This is due to stable configuration of nitrogen (halffilled 2 p -orbital). Due to screening effect the valency electron experiences less attraction towards the nucleus. This brings decrease in the nuclear charge (Z) actually present on the nucleus. The reduced nuclear charge is termed effective nuclear charge and its magnitude increases in a period when we move from left to right.

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