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Question: Answered & Verified by Expert
Arrange $L \dot{I}, \mathrm{Be}, \mathrm{B}$ and $\mathrm{C}$ in decreasing order of their first ionisation enthalpies.
ChemistryClassification of Elements and Periodicity in PropertiesAP EAMCETAP EAMCET 2020 (22 Sep Shift 1)
Options:
  • A Li $>$ B $>$ Be $>$ C
  • B C $>$ Li $>$ Be $>$ B
  • C $\mathrm{C}>\mathrm{Be}>\mathrm{B}>\mathrm{Li}$
  • D $\mathrm{C}>\mathrm{B}>\mathrm{Be}>\mathrm{Li}$
Solution:
2407 Upvotes Verified Answer
The correct answer is: $\mathrm{C}>\mathrm{Be}>\mathrm{B}>\mathrm{Li}$
As we go from left to right in period the ionisation potential increases but $\mathrm{Be}$ and $\mathrm{B}$ are exception as the Be has $1 s^2, 2 s^2$ and boron has $1 s^2, 2 s^2, 2 p^1$ so it's easy to remove electron from boron than berylium decreasing order of their first ionisation enthalpies.
$$
\mathrm{C}>\mathrm{Be}>\mathrm{B}>\mathrm{Li}
$$
So, option (3) is correct.

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