Question

Which one of the following Lanthanoids does not form ${\mathrm{MO}}_2$? [M is Lanthanoid metal]

• A. $\mathrm{Nd}$
• B. $\mathrm{Yb}$
• C. $\mathrm{Dy}$
• D. $\mathrm{Pr}$

Answer 1

The correct option is B

$\mathrm{Yb}$

The correct option is (b).

The correct answer's explanation:

(b)

• Explanation: $\mathrm{Yb}\left(70\right)=4{\mathrm{f}}^{14}6{\mathrm{s}}^2$The ionic radius, which decreases steadily from Lanthanum to Lutetium, governs the chemistry of all lanthanide elements.
• Because they are chemically similar to lanthanum, these elements are known as lanthanides. Lanthanides are devoid of magnetic, color, and spectral properties.
• If $\mathrm{Yb}$ has a fully filled orbital and will require more energy as a result of reaching an $+4$oxidation state.
  ${\mathrm{MO}}_2$type oxide does not form $\mathrm{Yb}$

The reason for the incorrect answer:

Options b, c, and d:

1. Lanthanum is sometimes considered a d-block element because it has one electron in a d orbital but no electrons in an f orbital. It has also been argued that because the term lanthanide literally means lanthanide atom.
2. $\mathrm{Nd}:\left[\mathrm{Xe}\right]4\mathrm{f}⁴6\mathrm{s}²$, $\mathrm{Dy}:\left[\mathrm{Xe}\right]4{\mathrm{f}}^{10}6{\mathrm{s}}^2$ , and $\mathrm{Pr}:\left[\mathrm{Xe}\right]4{\mathrm{f}}^{3}6{\mathrm{s}}^2$ do not produce oxides with ${\mathrm{MO}}_2$. Lanthanides have a low tendency to form complexes due to their low charge density and small size.
3. However, as the atomic number increases, so do the proclivity and stability of complexes.

The correct answer is B: It has a fully filled orbital and will require more energy as a result.