Question

Choose an incorrect statement about the properties of lanthanides.

• A. Except Promethium all are nonradioactive in nature
• B. The atomic and ionic radii decrease from lanthanum to lutetium.
• C. Binding to water is common
• D. Coordination numbers usually less than 6.

Hint:

Lanthanide ions are large, so they prefer high coordination numbers.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
Lanthanoids show the lanthanoid contraction and form ions that are large and strongly hydrated.

Step 2: Check each statement
Only promethium is radioactive among them, so (A) is correct.
Atomic and ionic radii decrease from La to Lu, so (B) is correct.
Lanthanide ions bind water readily, so (C) is correct.

Step 3: The incorrect statement
Because the ions are large, lanthanides usually show high coordination numbers such as 8 or 9, not less than 6. So (D) is incorrect.

Final Answer:
The incorrect statement is that coordination numbers are usually less than 6. \[ \boxed{\text{(D) }\text{Coordination numbers usually less than 6.}} \]