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Question
The order of decreasing ionisation enthalpy in alkali metals is ______.
Options
Na > Li > K > Rb
Rb < Na < K < Li
Li > Na > K > Rb
K < Li < Na < Rb
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Solution
The order of decreasing ionisation enthalpy in alkali metals is Li > Na > K > Rb.
Explanation:
On moving down the group as the size increases, the nuclear charge attraction decreases. The effect of increasing size outweighs the increasing nuclear charge. Thus, ionization enthalpy decreases. The order of decreasing ionization enthalpy is Li > Na > K > Rb
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