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Assertion : In the series Sc to Zn, the ...

Assertion : In the series Sc to Zn, the enthalpy of atomisation of zinc is the lowest.
Reason : Zinc has greater number of unpaired electrons.

A

If both (A) and (R) are correct and (R) is the correct explanation of(A).

B

If both (A) and (R) are correct, but(R) is not the correct explanation of (A).

C

If(A) is correct, but (R) is incorrect.

D

If both (A) and (R) are incorrect.

Text Solution

Verified by Experts

The correct Answer is:
C
Zinc does not have unpaired electrons in ground state as well as in its common oxidātion state.
Enthalpy of atomisation depends upon the number of unpaired electrons. Greater the number of unpaired electrons, stronger is the interatomic metallic bonding and higher is the enthalpy of atomisation
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Presence of unpaired electrons makes a species paramagnetic. Each unpaired electron has a magnetic moment associated with its spin angular momentum and orbital angular momentum. For the compounds of the first series of transition metals, the contribution of the orbital angular momentum is effectively quenched and hence is considerably important. For these, the magnetic moment is determined by the number of unpaired electrons and is calculated by using the spin-only formula, i.e., mu = sqrt(n(n+2)) where n=number of unpaired electrons and mu =magnetic momentin (in Bohr magneton, B.M.). If n=1, then mu = 1.73 B.M . Which one of the following transition metal ions is paramagnetic?

Presence of unpaired electrons makes a species paramagnetic. Each unpaired electron has a magnetic moment associated with its spin angular momentum and orbital angular momentum. For the compounds of the first series of transition metals, the contribution of the orbital angular momentum is effectively quenched and hence is considerably important. For these, the magnetic moment is determined by the number of unpaired electrons and is calculated by using the spin-only formula, i.e., mu = sqrt(n(n+2)) where n=number of unpaired electrons and mu =magnetic momentin (in Bohr magneton, B.M.). If n=1, then mu = 1.73 B.M . The magnetic moment of a transition metal ion is found to be 3.87 B.M. The number of unpaired electrons present in it is:

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