Consider the following statements regarding the first ionization enthalpies of elements: I. Beryllium has a higher first ionization enthalpy than boron. II. Oxygen has a higher first ionization enthalpy than nitrogen. III. Magnesium has a higher first ionization enthalpy than sodium. IV. Sulphur has a higher first ionization enthalpy than phosphorus. Which of the given statements are correct?

Step-by-step solution

Statement I: The electronic configuration of Be is 1s² 2s² and that of B is 1s² 2s² 2p¹ . The 2s orbital is fully filled and more penetrating than the 2p orbital. Thus, removing an electron from Be requires more energy than from B. Statement I is correct. Statement II: The electronic configuration of N is 1s² 2s² 2p³ and that of O is 1s² 2s² 2p⁴ . Nitrogen has a stable half-filled p -orbital, making its first ionization enthalpy higher than that of oxygen. Statement II is incorrect. Statement III: Magnesium ( 3s² )