Assertion : Magnetic moment of Dy is highest | vedclass

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Question

In lanthanide ions the $4fe^-$ are well shielded from external field by the overlying $5s$ and $5p$ electrons. Thus the magnetic effect of the motion

Vedclass · Accepted Answer

If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

Vedclass · Answer

In lanthanide ions the $4fe^-$ are well shielded from external field by the overlying $5s$ and $5p$ electrons. Thus the magnetic effect of the motion of the electron in its orbital is not quenched put, Thus the magnetic moment must be calculated taking into account both the magnetic momeent from unpaired $e^-$ spins and that from orbital motion.

$\mu \, = \,g\sqrt {J(J\, + \,1)} $

Where $g\, = \,1\frac{1}{2} + \,\frac{{S(S + 1)\, - \,L(L + 1)}}{{2J\,(J + 1)}}$

$J=L-S$ when the shell is less than half fill $=L+S$ when the shell is more than half fill.

In $Dy^{3+}\,([Xe]4f^9)$  $f-$ level is more than half fill hence spin and orbital motion work together, highest in lanthanoids.

Hence, both assertion and reason are true and reason is correct explanation of assertion.

Assertion : Magnetic moment of $Dy$ is highest among lanthanoids.

Reason : Orbital motion contributes magnetic moment.

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Assertion : Magnetic moment of $Dy$ is highest among lanthanoids. Reason : Orbital motion contributes magnetic moment.