Question

The first ionisation potential (in eV) of Be and B, respectively are

• A. 8.29, 9.32
• B. 9.32, 9.32
• C. 8.29, 8.29
• D. 9.32, 8.29

Answer 1

Answer: (D)

First ionisation potential of Be is greater than
boron due to stable configuration
${}_{4}Be=1s^2,2s^2$
${}_{5}B=1s^2,2s^{2}2p^1$
Order of attraction of electrons towards nucleus is $2s>2p$, so more amount of energy is required to remove the electron from $2s$ orbital in comparison to $2p$ orbital.
So, ionisation potential of $Be$ is $9.32eV$ and $B$ is $8.29eV$