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Given below are two statements:
Statement I: Ferromagnetism is considered as an extreme form of paramagnetism.
Statement II: The number of unpaired electrons in a $\text{Cr}^{2+}$ ion ($Z=24$) is the same as that of a $\text{Nd}^{3+}$ ion ($Z=60$).
In the light of the above statements, choose the correct answer from the options given below:
Statement I: Ferromagnetism is considered as an extreme form of paramagnetism.
Statement II: The number of unpaired electrons in a $\text{Cr}^{2+}$ ion ($Z=24$) is the same as that of a $\text{Nd}^{3+}$ ion ($Z=60$).
In the light of the above statements, choose the correct answer from the options given below:
A
Both Statement I and Statement II are true
B
Both Statement I and Statement II are false
C
Statement I is true but Statement II is false
D
Statement I is false but Statement II is true
Explanation
Statement I is true (ferromagnetism arises from spontaneously parallel aligned magnetic domains). Statement II is false: $\text{Cr}^{2+}$ ($3d^4$) has 4 unpaired electrons, while $\text{Nd}^{3+}$ ($4f^3$) has 3 unpaired electrons.
Detailed Solution
Statement I is true: Ferromagnetism occurs when individual paramagnetic atomic magnetic dipoles interact via quantum exchange coupling and spontaneously align in parallel domains, representing an extreme form of paramagnetism. Statement II is false: $\text{Cr}$ ($Z = 24$) has ground state $[\text{Ar}]3d^5 4s^1$, so $\text{Cr}^{2+}$ is $[\text{Ar}]3d^4$ possessing 4 unpaired electrons. Neodymium ($\text{Nd}, Z = 60$) has ground state $[\text{Xe}]4f^4 6s^2$, so $\text{Nd}^{3+}$ is $[\text{Xe}]4f^3$ possessing 3 unpaired electrons. The numbers of unpaired electrons are 4 and 3, respectively, which are not the same.