Question

If first ionization enthalpy of Mg is \(738 \, \text{kJ/mol\) then second ionization enthalpy of Mg in kJ/mol will be :

• A. \(-640 \, \text{kJ/mol}\)
• B. \(-527 \, \text{kJ/mol}\)
• C. \(658 \, \text{kJ/mol}\)
• D. \(1450 \, \text{kJ/mol}\)

Answer 1

The Correct Option is D

Concept: Ionization enthalpy is the energy required to remove an electron from a gaseous atom or ion. Successive ionization energies always increase because: • Effective nuclear charge on remaining electrons increases.
• Size of the ion decreases after removal of an electron.
• Attraction between nucleus and electrons becomes stronger.
Step 1: Write the ionization processes. First ionization: \[ Mg(g) \rightarrow Mg^{+}(g) + e^- \] \[ IE_1 = 738 \, \text{kJ/mol} \] Second ionization: \[ Mg^{+}(g) \rightarrow Mg^{2+}(g) + e^- \]
Step 2: Compare successive ionization energies. Since electron is removed from a positively charged ion, more energy is required. \[ IE_2 > IE_1 \]
Step 3: Select correct option. Among the given values, only \(1450 \, \text{kJ/mol}\) is greater than \(738 \, \text{kJ/mol}\). Thus, \[ \boxed{IE_2 = 1450 \, \text{kJ/mol}} \]