Question

What is diamagnetism?

Answer 1

Diamagnetism is a quantum mechanical effect where the lack of unpaired electrons allows for an induced magnetic field that repels an applied magnetic field. In other words, apply a magnetic field onto a diamagnetic substance and it slightly resists it.

This effect is generally weak, and if a substance is paramagnetic (has unpaired electrons), it usually will render the diamagnetism insignificant.

To determine diamagnetism:

1. Write out the electron configuration.
2. See if for any orbitals, the number of electrons is `1`.
3. If so, the substance is paramagnetic. If not, it is diamagnetic.

`"Co"` has a configuration of `[Ar]3d^7 4s^2`. Since there are five `3d` orbitals, then according to Hund's rule, three orbitals have unpaired electrons, and two have paired electrons.

(`2 + 2 + 1 + 1 + 1 = \mathbf(7)` electrons in the `3d` subshell, as stated from the electron configuration.)

Thus, `"Co"` is paramagnetic.

CHALLENGE: Can you see that `Zn` is diamagnetic?