Chemistry Q60 – JEE-MAIN 2026

Home Chemistry Periodicity & ElementsQuestion #504

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:

Clue 1 of 3: Stability of Oxidation States and Redox Properties

Consider the general trends in stability of higher oxidation states for transition metals and the redox behavior of f-block ions based on their electron configurations.

🧠 Full Solution Path

Step 1: Evaluate Statement A and B✦ Active

Statement A: For Group 6 elements, the stability of higher oxidation states increases down the group. Thus, Mo(VI) and W(VI) are more stable than Cr(VI). Therefore, statement A is false.

Statement B: $C e^{4 +}$ has an $f^{0}$ configuration and tends to gain an electron to form $C e^{3 +}$ ( $f^{1}$ ), acting as an oxidant. $T b^{4 +}$ has an $f^{7}$ configuration and tends to gain an electron to form $T b^{3 +}$ ( $f^{8}$ ), acting as an oxidant. $E u^{2 +}$ has an $f^{7}$ configuration and tends to lose an electron to form $E u^{3 +}$ ( $f^{6}$ ), acting as a reductant. $Y b^{2 +}$ has an $f^{14}$ configuration and tends to lose an electron to form $Y b^{3 +}$ ( $f^{13}$ ), acting as a reductant. Therefore, statement B is true.

Step 2: Evaluate Statement C and D○ Expand

Statement C: The ground state electronic configuration of neutral Americium (Am, Z=95) is $[R n] 5 f^{7} 7 s^{2}$ , which has 7 unpaired electrons. The ground state electronic configuration of neutral Curium (Cm, Z=96) is $[R n] 5 f^{7} 6 d^{1} 7 s^{2}$ , which has 8 unpaired electrons (7 from $5 f$ and 1 from $6 d$ ). Therefore, statement C is false.

Statement D: Actinoid contraction is generally greater than lanthanoid contraction. This is because $5 f$ electrons provide poorer shielding of the nuclear charge compared to $4 f$ electrons, leading to a stronger effective nuclear charge and thus a greater contraction across the actinide series. Therefore, statement D is true.

Step 3: Identify Correct Option○ Expand

Based on the evaluation, statements B and D are correct. This corresponds to option 3.

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Chemistry Question 60 – JEE-MAIN 2026

Clue 1 of 3: Stability of Oxidation States and Redox Properties

🧠 Full Solution Path