Question

The increasing order of the first ionisation enthalpies of the elements B, P, S and F (lowest first) is

• A. $F
• B. $P
• C. $B
• D. $B

Answer 1

Answer: (D)

$B

Answer 2

In general as we move from left to right in a period, the ionisation enthalpy increases with increasing atomic number. The ionisation enthalpy decreases as we move down a group. P$\left(1s^{2}2s^{2}2p^{6}3s^{2}3p^{3}\right)$ has a stable half filled electronic configuration hence, its ionisation enthalpy is higher than that of S. $\therefore\,$ Increasing order of ionization energy is $B