A paramagnetic substance has unpaired electrons and will consequently be attracted to an external magnetic field.
For example, if you bring an iron nail into the presence of an external magnetic field,
you'll induce a magnetic field in the iron and it will be attracted to the magnet.
Silver is paramagnetic because it has at least one unpaired electron in its electron configuration.
A diamagnetic substance has no unpaired electrons and consequently will not be attracted to an external magnetic field.
All of the electrons in zinc are paired so zinc is diamagnetic.
When we create an electron configuration for zinc two plus,
it's important that we remove the electrons first from the orbitals with the highest principal quantum number which is from the 4s subshell.
After removing these electrons, the electron configuration is Argon 3d10.
All of the electrons in zinc two plus are still paired so zinc two plus is also diamagnetic.
Let's practice by writing the electron configuration for these two ions
and determining if they are paramagnetic or diamagnetic.
To get the electron configuration for chromium three plus,
let's start with the electron configuration for just chromium.
It is Argon 4s1 3d5.
Chromium is one of our exceptions which moves one of the electrons from the s subshell and half fills the d subshell.
To create the electron configuration for chromium three plus, we'll remove three electrons.
We remove the one electron in the 4s subshell first
and remove the other two electrons from the 3d subshell.
If we create the orbital diagram for chromium three plus,
we see we have three unpaired electrons so chromium three plus is paramagnetic.
To get the electron configuration for cadmium two plus, let's start with the electron configuration for cadmium.
It's Krypton 5s2 4d10.
To create the electron configuration for cadmium two plus, we'll remove two electrons.
The 5s subshell has the highest principal quantum number, so we'll remove these two electrons first.
Our electron configuration for cadmium two plus is Krypton 4d10.
From the orbital diagram, we see all of our electrons are paired so cadmium two plus is diamagnetic.
Considering the size of ions, cations are smaller than their neutral atoms and anions are larger than their neutral atoms.
We can see this by comparing sizes of neutral atoms, cations, and anions of various elements.
We can practice by ranking ions according to increasing radius.
If we look closely at this set of ions, we should notice that all of these ions have 10 electrons.
A group of ions with the same number of electrons is called and isoelectric series.
In an isoelectric series, the ion with the most protons is the smallest and the ion with the least number of protons is the largest.
If we arrange these ions in order of increasing size, the smallest will be aluminum three plus
because it has the most protons, and the largest will be oxygen two minus because it has the fewest protons.