Consider the following statements regarding ionization enthalpy: (I) The first ionization enthalpy of Beryllium is greater than that of Boron. (II) The second ionization enthalpy of Sodium is lower than that of Magnesium. (III) The first ionization enthalpy of Nitrogen is greater than that of Oxygen. (IV) First ionization enthalpy generally decreases from left to right across a period. How many of the above statement

Step-by-step solution

Let us evaluate each statement: Statement (I) is correct. Beryllium ( 1s² 2s² ) has a fully filled 2s subshell, which is more stable and has a greater penetration effect than the 2p¹ electron in Boron ( 1s² 2s² 2p¹ ). Thus, Be has a higher first ionization enthalpy than B. Statement (II) is incorrect. After losing one electron, Sodium forms Na ⁺ which has a highly stable noble gas core configuration ( 1s² 2s² 2p⁶ ). Magnesium forms Mg ⁺ ( 1s² 2s² 2p⁶ 3s¹ ). Removing a second electron from the stable core of Na ⁺ re