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Question: Answered & Verified by Expert
The order of decreasing ionisation enthalpy in alkali metals is
Chemistrys Block Elements
Options:
  • A
    $\mathrm{Na}>\mathrm{Li}>\mathrm{K}>\mathrm{Rb}$
  • B
    $\mathrm{Rb} < \mathrm{Na} < \mathrm{K} < \mathrm{Li}$
  • C
    $\mathrm{Li}>\mathrm{Na}>\mathrm{K}>\mathrm{Rb}$
  • D
    $\mathrm{K} < \mathrm{Li} < \mathrm{Na} < \mathrm{Rb}$
Solution:
2345 Upvotes Verified Answer
The correct answer is:
$\mathrm{Li}>\mathrm{Na}>\mathrm{K}>\mathrm{Rb}$
On moving down the group from Li to Rb, increased atomic radii makes the removal of electron easier. Thus, the order of decreasing ionization enthalpy will be: $\mathrm{Li}>\mathrm{Na}>\mathrm{K}>\mathrm{Rb}$
Also, LiF exhibit very high lattice energy.

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