d and f BLOCK ELEMENTS MCQ Quiz: GKFix - Bridge of Knowledge

Question 71

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Which lanthanoid elements are known to commonly exhibit a +4 oxidation state, and what feature of their electronic configuration contributes to this?

Only Lutetium (Lu); achieving a filled 4f^14 subshell.
Ce (Cerium), Pr (Praseodymium), Nd (Neodymium), Tb (Terbium), and Dy (Dysprosium); losing electrons to achieve a stable [Xe] noble gas core or half-filled f-subshell.
All lanthanoids can exhibit +4.
Only Promethium (Pm); due to its radioactive nature.

Question 72

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What is the electronic configuration of the Ce^3+ ion, and how many unpaired electrons does it have according to Hund's rule?

[Xe] 4f^2; 2 unpaired electrons.
[Xe] 4f^0; 0 unpaired electrons.
[Xe] 4f^1; 1 unpaired electron.
[Xe] 5d^1; 1 unpaired electron.

Question 73

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Why are the 5f electrons in the actinoid series less effective at shielding the outer electrons from the nuclear charge compared to 4f electrons in lanthanoids?

The 5f electrons are closer to the nucleus.
The 5f electrons are completely filled.
The 5f electrons themselves provide poor shielding from element to element in the series.
The 5f electrons have lower energy than 4f electrons.

Question 74

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Why does Cu^+ disproportionate in aqueous solution?

Because Cu^+ is unstable in any environment.
Because the E0 value for the disproportionation reaction is favorable.
Because Cu^+ is more stable than Cu^2+.
Because Cu^+ is a strong oxidizing agent.

Question 75

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Why is Cr^2+ a stronger reducing agent than Fe^2+?

Cr^2+ has fewer electrons than Fe^2+.
Cr^2+ gets oxidized to the more stable d^3 configuration (Cr^3+), while Fe^2+ gets oxidized to the less stable d^5 configuration (Fe^3+).
Fe^2+ has a higher atomic number.
Cr^2+ is more electronegative than Fe^2+.

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