JEE Main Chemistry Question (2026) — Solution

Step-by-step solution

Ionization enthalpy is the energy required to remove an electron from an isolated gaseous atom or ion. It is always an endothermic process, so its value is always positive. The second ionization enthalpy is the energy required to remove an electron from a unipositive ion. Since the effective nuclear charge increases after the removal of the first electron, the remaining electrons are held more tightly by the nucleus. Thus, the second ionization enthalpy is always greater than the first ionization enthalpy (IE_ 2 > IE_ 1 ). Given the first ionization enthalpy of Mg is +737 kJ/mol, the second ionization enthalpy must be positive and greater than +737 kJ/mol. Among the given options, only +1450 kJ/mol satisfies these conditions. Answer: +1450 kJ/mol