MolSynapsequestion bank

MolSynapse / Question bank / d- and f-Block Elements / Lanthanoids and lanthanoid contraction

JEE Advanced levelSingle correct optionDifficulty 3 of 3df200

For which of the following pairs of ions is the spin-only magnetic moment identical? (Atomic numbers: Ce 58, Nd 60, Sm 62, Eu 63, Gd 64, Dy 66, Ho 67)

A $Sm X^{3 +}$ and $Dy X^{3 +}$
B $Ce X^{3 +}$ and $Pr X^{3 +}$
C $Eu X^{3 +}$ and $Gd X^{3 +}$
D $Nd X^{3 +}$ and $Ho X^{3 +}$

Answer: A

Sm X^{3 +}

is

4 f^{5}

(5 unpaired) and

Dy X^{3 +}

is

4 f^{9}

: seven electrons singly and two paired, leaving 5 unpaired. Both give

35 = 5.92

BM. In the other pairs the unpaired counts differ: Eu/Gd 6 and 7, Ce/Pr 1 and 2, Nd/Ho 3 and 4.

Practice d- and f-Block Elements More on Lanthanoids and lanthanoid contraction

Previous questionNext question

More questions on Lanthanoids and lanthanoid contraction