Question

Among the following, the element of highest first ionisation enthalpy is

• A. $C$
• B. $F$
• C. $Be$
• D. $N$
• E. $Ne$

Answer 1

Answer: (E)

The electronic configuration of the given elements is as

${}_{6}C=1s^2,2s^2,2p^2$

${}_{9}F=1s^2,2s^2,2p^5$

${}_{4}Be=1s^{2}2s^2$

$7N=1s^2,2s^{2}2p^3$

$10Ne=1s^2,2s^2,2p^6$

Thus, Ne has the highest ionisation enthalpy because of its completely filled configuration and high effective nuclear charge.