Question

Is $C{o^{3 + }}$ paramagnetic or diamagnetic?

Answer 1

To find whether a given ion is paramagnetic or diamagnetic, we have to count the number of unpaired electrons. To find the number of unpaired electrons, we have to write the electronic configuration of the ion.

Complete answer:
A paramagnetic substance is defined as a substance which contains at least one unpaired electron. A diamagnetic substance is defined as a substance which has only paired electrons i.e. no unpaired electrons. If two electrons share the same orbital, their spin quantum numbers have to be different. Whenever two electrons are paired together in an orbital i.e. when their total spin is zero, they are said to be diamagnetic electrons. Atoms with all diamagnetic electrons are said to be diamagnetic atoms. A paramagnetic electron is an unpaired electron. An atom or ion is said to be paramagnetic even if one orbital has a net spin. An atom or ion could have ten diamagnetic electrons, but as long as it has one paramagnetic electron, it is considered to be paramagnetic. The electronic configuration of the element cobalt is $[{\text{Ar]3}}{{\text{d}}^7}4{{\text{s}}^2}$ and the electronic configuration of the ion $C{o^{3 + }}$ is $[{\text{Ar]3}}{{\text{d}}^6}$ . Here, there are two paired electrons and four unpaired electrons. So, we can say that the ion $C{o^{3 + }}$ is paramagnetic.
Therefore, $C{o^{3 + }}$ is paramagnetic.

Note:
Remember that electrons are first removed from $4s$ when cobalt forms $C{o^{3 + }}$ . First two electrons are removed from $4s$ and one electron is removed from $3d$ . Diamagnetic atoms are slightly repelled from a magnetic field whereas paramagnetic atoms are slightly attracted to a magnetic field.