Question

The \( 1^{\text{st}} \) ionization enthalpy for Mg is +737 kJ/mol. The most probable estimated value of the \( 2^{\text{nd}} \) ionization enthalpy of Mg is _______ kJ/mol.

• A. \( -906 \text{ kJ/mol} \)
• B. \( -856 \text{ kJ/mol} \)
• C. \( +1450 \text{ kJ/mol} \)
• D. \( +590 \text{ kJ/mol} \)

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ionization enthalpy is the energy needed to remove an electron from a gaseous atom or ion. Successive ionization enthalpies (\( IE_1, IE_2, \dots \)) always increase because it becomes harder to remove an electron from an increasingly positively charged ion.

Step 2: Key Formula or Approach:
Always \( IE_2>IE_1 \). For Group 2 elements like Mg, \( IE_2 \) is usually significantly higher but not as extremely high as \( IE_3 \) (which would break a noble gas core).

Step 3: Detailed Explanation:
- \( IE_1 \) of Mg = 737 kJ/mol.
- \( IE_2 \) must be greater than 737.
- (A) and (B) are negative, but ionization is an endothermic process (energy must be provided), so these are impossible.
- (D) 590 is less than 737, violating the trend.
- (C) 1450 is a reasonable increase from 737. For Magnesium, actual experimental \( IE_2 \) is approx. 1451 kJ/mol.

Step 4: Final Answer:
The estimated value is +1450 kJ/mol.