Q8 / 180 · KCET 2011 · Chemistry

Generally, the first ionisation energy increases along a period. But there are some exceptions. The one which is not an exception is

  • A
    Be and B
  • Correct answer
    B
    Na and Mg
  • C
    $\mathrm{Mg}$ and $\mathrm{Al}$
  • D
    $\mathrm{N}$ and $\mathrm{O}$

Solution

First ionisation energy of $\mathrm{Mg}$ is more than that of $\mathrm{Na}$. It is not an exception.

Hence, the correct answer is option: 'B'.

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