JEE Main 2026 — Classification of Elements and Periodicity in Properties Question with Solution
JEE Main 2026 (04 April Shift 2)
Question
The ionization enthalpy for Mg is kJ/mol. The most probable estimated value of the ionization enthalpy of Mg is ______.
Choose an option
Show full solutionCorrect option: C
Correct answer
C kJ/mol
Step-by-step explanation
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 ().
Given the first ionization enthalpy of Mg is kJ/mol, the second ionization enthalpy must be positive and greater than kJ/mol.
Among the given options, only kJ/mol satisfies these conditions.
Answer: kJ/mol
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 ().
Given the first ionization enthalpy of Mg is kJ/mol, the second ionization enthalpy must be positive and greater than kJ/mol.
Among the given options, only kJ/mol satisfies these conditions.
Answer: kJ/mol
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This is a previous-year question from JEE Main 2026, covering the Classification of Elements and Periodicity in Properties chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.