Question

Which of the following statement is INCORRECT

• A. The actinoids show in general +3 oxidation state.
• B. Actinoids are less reactive metals.
• C. The magnetic properties of actinoids are more complex than those of lanthanoids.
• D. Hydrochloric acid attacks actinoids.
• E. Nitric acid slightly attacks actinoids.

Hint:

Reactivity increases along the actinoid series initially. They are all radioactive and chemically reactive.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
This question tests general knowledge about the properties of actinoids, a series of f-block elements. We need to evaluate each statement to find the incorrect one.
Step 2: Detailed Explanation
(A) The actinoids show in general +3 oxidation state. This is a correct statement. Like lanthanoids, the most common and stable oxidation state for actinoids is +3. However, actinoids also show a wider range of oxidation states (e.g., up to +7 for Np and Pu) because the 5f, 6d, and 7s orbitals have comparable energies.
(B) Actinoids are less reactive metals. This is an incorrect statement. Actinoids are highly reactive, electropositive metals. They are even more reactive than lanthanoids. They react with boiling water and non-metals readily. When finely divided, they can be pyrophoric (ignite spontaneously in air).
(C) The magnetic properties of actinoids are more complex than those of lanthanoids. This is a correct statement. The 5f electrons in actinoids are less shielded and more involved in bonding than the 4f electrons in lanthanoids. This leads to more complex magnetic behavior that is not as easily explained by simple models as it is for lanthanoids.
(D) Hydrochloric acid attacks actinoids. This is a correct statement. Being highly reactive metals, actinoids are readily attacked by most common acids, including HCl, to produce hydrogen gas.
(E) Nitric acid slightly attacks actinoids. This is a correct statement. Although nitric acid is a strong acid, it often forms a thin, protective (passive) oxide layer on the surface of the actinoid metals, which prevents further reaction. This makes the attack appear slight or slow.
Step 3: Final Answer
The statement that actinoids are less reactive metals is incorrect; they are in fact highly reactive.