Periodic Classification and Periodic Properties 2 Question 46

46. Explain the following :

“The first ionisation energy of carbon atom is greater than that of boron atom whereas, the reverse is true for the second ionisation energy.”

(1989, 2M)

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Solution:

  1. The first ionisation energy of carbon is greater than the same of boron as predicted from periodic trend. However, for 2nd

<img src=“https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/7a8b51a7-7de1-415e-9da3-884d19b92700/public"width="450">

ionisation trend is reversed due to stability of completely filled $2 s$-orbital of $\mathrm{B}^{+}$:



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