Q60 / 160 · JIPMER 2006 · Chemistry

What will be the order of Ist ionisation energy ?

  • Correct answer
    A
    $\mathrm{Li}\gt\mathrm{Na}\gt\mathrm{K}$
  • B
    $\mathrm{K}\gt\mathrm{Li}\gt\mathrm{Na}$
  • C
    $\mathrm{Na}\gt\mathrm{Li}\gt\mathrm{K}$
  • D
    $\mathrm{Li}\gt\mathrm{K}\gt\mathrm{Na}$

Solution

In a sub-group ionisation energy decreases from top to bottom because atomic size increases. So, the Ist IE of $\mathrm{Li}, \mathrm{Na}$ and K are in the order $\mathrm{Li}\gt\mathrm{Na}\gt\mathrm{K}$.

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

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