The correct increasing order of first ionization enthalpy for the elements Si , P , S , and Cl is:

Step-by-step solution

Across a period, the first ionization enthalpy generally increases with an increase in atomic number due to increasing effective nuclear charge. However, Phosphorus ( P ) has a stable half-filled 3p orbital configuration ( [ Ne ] 3s^2 3p^3 ), whereas Sulphur ( S ) has a 3p^4 configuration ( [ Ne ] 3s^2 3p^4 ). Removing an electron from the stable half-filled p -orbital of P requires more energy than removing the paired electron from the p -orbital of S . Thus, the first ionization enthalpy of P is greater than that