Question

Amongst the following, select the element with highest ionisation enthalpy

• A. Sodium
• B. Potassium
• C. Beryllium
• D. Magnesium

Answer 1

The correct option is C

Beryllium

Part 1: Explanation for Correct answer

Option (c) Beryllium

• Berrylium has the smallest size amongst the other elements mentioned.
• Hence its nuclear force of attraction is greater than the others.
• Therefore its Ionisation enthalpy is greater than Magnesium, Sodium and Potassium

Part 2: Incorrect answers:- (a) Sodium

• Its size is greater than Beryllium
• Hence its nuclear force of attraction is lower than that of Beryllium.
• Therefore its ionisation enthalpy is less than Beryllium.

(b) Potassium

• Its size is greater than Beryllium
• Hence its nuclear force of attraction is lower than that of Beryllium, Sodium and Magnesium..
• Therefore its ionisation enthalpy is least among them.

(d) Magnesium

• Its size is greater than Beryllium
• Hence its nuclear force of attraction is lower than that of Beryllium.
• Therefore its ionisation enthalpy is less than Beryllium.

Final answer:- Option (c) Beryllium is the element with highest ionisation enthalpy.