What is diamagnetism?

1 Answer
Apr 6, 2016

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?