The correct statements among the following are, A. Mo(VI) and W(VI) are less stable than Cr(VI). B. Ce^ 4+ and Tb^ 4+ are oxidant while Eu^ 2+ and Yb^ 2+ are reductant. C. Cm and Am have seven unpaired electrons. D. Actinoid contraction is greater from element to element than lanthanoid contraction. Choose the correct answer from the options given below:
C. B and D Only
In d-block elements, the stability of higher oxidation states increases down a group. Therefore, Mo(VI) and W(VI) are more stable than Cr(VI). Statement A is incorrect. The most stable oxidation state for lanthanoids is +3. Ions like Ce^ 4+ and Tb^ 4+ tend to gain an electron to achieve the +3 state, acting as oxidants. Conversely, Eu^ 2+ and Yb^ 2+ tend to lose an electron to achieve the +3 state, acting as reductants. Statement B is correct. The electronic configuration of Am is [Rn] 5f^ 7 7s^ 2 , which has 7 unpaired electrons. The electronic configuration of Cm is [Rn] 5f^ 7 6d^ 1 7s^ 2 , which has 8 unpaired electrons (7 in 5f and 1 in 6d). Statement C is incorrect. The 5f electrons have a poorer shielding effect compared to 4f electrons. As a result, the effective nuclear charge increases more significantly across the actinoid series, leading to a greater actinoid contraction from element to element than the lanthanoid contraction. Statement D is correct. Thus, only statements B and D are correct. Answer: B and D Only
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