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KCET2012ChemistryClassification of Elements and Periodicity in Properties

The correct order of ionisation energy of C , N , O and F is

Options

  1. AC < N < O < F
  2. BC < O < N < F
  3. CF < O < N < C
  4. DF < N < C < O

Correct answer

B. C < O < N < F

Step-by-step solution

On moving from left to right in a period, ionisation energy increases. Thus, correct order of ionisation energy of C, N, O, F should be C < N < O < F But the ionisation energy of N is found to be greater than that of O. This is due to the presence of half-filled p-orbitals in N which provide it extra stability. Thus, the correct order is C < O < N < F .

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