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

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Solution:

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 has a stable half filled electronic configuration hence, its ionisation enthalpy is higher than that of S.
Increasing order of ionization energy is