Which among the following electronic configuration represents an atom with the lowest ionization enthalpy?
is stable electronic configuration due to half filled and fully-
filled p-orbitals respectively. Therefore, removing an electron from these atoms is difficult and thus, higher ionization enthalphy.
However, when an electron is removed from the atom having
configuration, it attains the stable configuration of fully filled p-orbital. Therefore, it
readily loses an electron (lowest ionization enthalpy).
Hence Option 2 is correct.