Question

Are the following ions diamagnetic or paramagnetic $?$ $C{r}^{3+}$ , $C{a}^{2+}$ , $N{a}^{+}$ , $Cr$ , $F{e}^{3+}$ .

Answer 1

Hint: First we know that the paramagnetic compounds (slats) generally contain transition metal ions which have one or more unpaired electrons in their electronic configuration. When electrons are paired together, their opposite spins cause their magnetic fields to cancel each other so no magnetic field exists (total spin is $0$ ). Thus, materials or ions with some unpaired electrons will have a magnetic field.

Complete answer:
Ions with all diamagnetic electrons are called diamagnetic ions. An atom is considered paramagnetic if even one orbital has a net spin.
To find if the given ions are paramagnetic or diamagnetic, write the electronic configurations of the atoms and check for unpaired electrons.

The electronic configuration of $Cr$ is $\left[Ar\right]3d^{5}4s^1$ . If three electrons are removed, $C{r}^{3+}$ is formed and its electronic configuration is $\left[Ar\right]3d^3$ . There are three unpaired electrons, so $C{r}^{3+}$ is paramagnetic.
Also $Cr$ is paramagnetic.

The electronic configuration of $Ca$ is $\left[Ar\right]4s^2$ . If two electrons are removed, $C{a}^{2+}$ is formed and its electronic configuration is $\left[Ar\right]$ . There are no unpaired electrons, so $C{a}^{2+}$ is diamagnetic.

The electronic configuration of $Na$ is $\left[Ne\right]3s^1$ . If one electron is removed, $N{a}^{+}$ is formed and its electronic configuration is $\left[Ne\right]$ . There are no unpaired electrons, so $N{a}^{+}$ is diamagnetic.

The electronic configuration of $Fe$ is $\left[Ar\right]3d^{6}4s^2$ . If one electron is removed, $F{e}^{3+}$ is formed and its electronic configuration is $\left[Ar\right]3d^5$ . There are five unpaired electrons, so $F{e}^{3+}$ is paramagnetic.
Therefore, $Cr$ , $C{r}^{3+}$ , $F{e}^{3+}$ ions are paramagnetic. And $N{a}^{+}$ , $C{a}^{2+}$ ions are diamagnetic.

Note:
Note that more unpaired electrons make the ion or molecule more paramagnetic. Because due to their spin the unpaired electrons have a magnetic dipole moment around each atom or molecule and act like tiny magnets. Also note that the electrons of an atom create a negative charge that balances the positive charge of the protons in the nucleus.