Question

Which of the following lanthanoid ions is diamagnetic?
[At. No. Ce=58, Sm=62, Eu=63, Yb=70]
A.$C{{e}^{4+}}$
B.$S{{m}^{2+}}$
C.$E{{u}^{2+}}$
D.$Y{{b}^{2+}}$

Answer 1

Diamagnetism of lanthanoid ions depends upon the presence of unpaired electrons on their valence shells. We also need to know about the electronic configuration of all the ions to find out about the diamagnetic properties.

Complete step by step solution:
Lanthanide ion is diamagnetic in nature, especially when there is no unpaired electron present.
$\begin{aligned} & C{{e}_{58}}=[Xe]4{{f}^{2}}5{{d}^{0}}6{{s}^{2}} \\\ & C{{e}^{2+}}=[Xe]4{{f}^{6}}5{{d}^{0}}6{{s}^{2}} \\\ & \\\ & S{{m}_{62}}=[Xe]4{{f}^{6}}5{{d}^{0}}6{{s}^{2}} \\\ & S{{m}^{2+}}=[Xe]4{{f}^{6}} \\\ & \\\ & E{{u}_{63}}=[Xe]4{{f}^{7}}5{{d}^{0}}6{{s}^{2}} \\\ & E{{u}^{2+}}=[Xe]4{{f}^{7}} \\\ & \\\ & Y{{b}_{70}}=[Xe]4{{f}^{14}}5{{d}^{0}}6{{s}^{2}} \\\ & Y{{b}^{2+}}=[Xe]4{{f}^{14}} \\\ \end{aligned}$
Hence, $Y{{b}^{2+}}$ is diamagnetic, due to the absence of the unpaired electron.

So the correct answer is option D.

Note: Lanthanoid is also called lanthanide which can be defined as any of the series of 15 consecutive chemical elements in the periodic table from lanthanum to lutetium (atomic numbers 57–71). With the elements scandium and yttrium, they make up the rare-earth metals. Lanthanides are also radioactive in nature.
Common Properties of the Lanthanides includes as follows:
-Silvery-white metals that tarnish when exposed to air, forming their respective oxides.
-They are generally soft metals.
-Moving from left to right across the period (according to increasing atomic number),we can observe that the radius of each lanthanide ${{3}^{+}}$ ion steadily decreases because of the lanthanoid contraction.
-They have got high melting points and boiling points.
-They are also very reactive.
Lanthanoid contraction which is also called lanthanide contraction, is, can be explained as the steady decrease in the size of the atoms and ions of the rare earth elements as of their increasing atomic number from lanthanum (atomic number 57) all the way to lutetium (atomic number 71). It is to be remembered that although lanthanides are very soft metals, they have a very good tendency to react. Several of the lanthanides form when there is a fission of uranium and plutonium.