Question

The set representing the correct order of first ionisation potential is

• A. \( K>Na>Li \)
• B. \( Be>Mg>Ca \)
• C. \( B>C>N \)
• D. \( Ge>Si>C \)

Hint:

Ionisation energy decreases down a group and generally increases across a period, with exceptions for groups 15 (half-filled stability) and 16.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Ionisation potential (IP) generally decreases down a group due to increasing atomic size.
Step 2: Detailed Explanation:
Option (A): \(K>Na>Li\) is incorrect. IP decreases down the group, so Li>Na>K. Option (B): \(Be>Mg>Ca\) is correct. IP decreases down Group 2. Option (C): \(B>C>N\) is incorrect. Across a period, IP generally increases, but there are exceptions. N has higher IP than O, and C has higher IP than B. The correct order is N>C>B. Option (D): \(Ge>Si>C\) is incorrect. IP decreases down the group, so C>Si>Ge.
Step 3: Final Answer:
The correct order is Be>Mg>Ca, option (B).