Paramagnetic Materials and Magnetic Moments

Paramagnetic materials are substances that are weakly attracted to a magnetic field. This attraction arises due to the presence of unpaired electrons in the material. These unpaired electrons have a magnetic moment associated with them, which can be either due to their orbital motion or their intrinsic spin.

Magnetic Moments of Electrons

The magnetic moment of an electron is a property that arises from its spin and orbital motion. The spin magnetic moment arises due to the intrinsic spin of the electron, while the orbital magnetic moment arises due to its motion around the nucleus.

Comparison of Magnetic Moments

To determine the relative magnitudes of the orbital and spin magnetic moments of electrons in paramagnetic materials, we can compare them to the Bohr magneton (μB). The Bohr magneton is a unit of magnetic moment that is used to describe the magnetic moments of atomic particles.

(A) Orbital and Spin Magnetic Moments of the Electrons are of the Order of Bohr Magneton

In paramagnetic materials, the orbital and spin magnetic moments of the electrons are of the order of the Bohr magneton. This means that their magnitudes are similar to or on the same scale as the Bohr magneton.

This is because the unpaired electrons in paramagnetic materials have both orbital and spin contributions to their magnetic moments. These contributions add up to give a total magnetic moment that is of the order of the Bohr magneton.

(B) Orbital Magnetic Moments of the Electrons are Zero

The statement that the orbital magnetic moments of the electrons in paramagnetic materials are zero is incorrect. In fact, the orbital motion of electrons around the nucleus gives rise to an orbital magnetic moment.

However, it is important to note that in some cases, the orbital magnetic moments of the electrons in paramagnetic materials may be small or negligible compared to their spin magnetic moments. This is because the orbital motion of the electrons may be restricted or their orbits may be highly symmetric, leading to a cancellation of the orbital magnetic moments.

(C) Orbital and Spin Magnetic Moments of the Electrons are Less than Zero

The statement that the orbital and spin magnetic moments of the electrons in paramagnetic materials are less than zero is incorrect. Magnetic moments are vectors and can have positive or negative values, depending on their orientation with respect to the magnetic field.

(D) Spin Magnetic Moments of the Electrons are Zero

The statement that the spin magnetic moments of the electrons in paramagnetic materials are zero is incorrect. The spin of the electrons gives rise to a spin magnetic moment, which is a fundamental property of the electron.

In paramagnetic materials, the presence of unpaired electrons leads to a net spin magnetic moment for the material as a whole. This spin magnetic moment is responsible for the weak attraction of paramagnetic materials to a magnetic field.

Conclusion

In summary, the correct statement is that in paramagnetic materials, the orbital and spin magnetic moments of the electrons are of the order of the Bohr magneton. The orbital magnetic moments are not zero, and the spin magnetic moments are not zero.