Question

The incorrect statement among the following is

• A. Actinoids are highly reactive metals, especially when finely divided
• B. Actinoid contraction is greater for element-to-element than Lanthanoid contraction.
• C. Most of the trivalent Lanthanoid ions are colorless in the solid state.
• D. Lanthanoids are good conductors of heat and electricity

Answer 1

The Correct Option is A

To determine the incorrect statement among the given options, let's analyze each statement related to actinoids and lanthanoids:

1. Statement A: "Actinoids are highly reactive metals, especially when finely divided."
   • Actinoids are indeed highly reactive metals, similar to how finely divided metals in general show increased reactivity. Therefore, this statement is correct.
2. Statement B: "Actinoid contraction is greater for element-to-element than Lanthanoid contraction."
   • Both actinoids and lanthanoids exhibit contraction. However, the contraction in actinoids is more pronounced because of poor shielding by f-electrons and increased nuclear charge. Thus, this statement is correct.
3. Statement C: "Most of the trivalent Lanthanoid ions are colorless in the solid state."
   • This is incorrect. Most trivalent lanthanoid ions show characteristic colors due to f-f transitions. Therefore, this statement is incorrect.
4. Statement D: "Lanthanoids are good conductors of heat and electricity."
   • Lanthanoids, being metals, generally have good electrical conductivity. This statement is correct.

Upon reviewing, it is clear that Statement C is actually incorrect. However, focusing on the provided correct answer choice (Statement A), there seems to be a discrepancy. By the typical accepted knowledge, option regarding the color of trivalent lanthanoid ions (Statement C) is the incorrect one among the provided options.