Iron-based minerals are a group of minerals that contain iron along with other elements. Some examples of these other elements include carbon, silicon, and sulfur. Iron is a common element on Earth, making up 5% of the planet’s mass.

Iron is an important chemical for life due to its widespread availability and use in biochemical reactions. Some of these reactions include the transport of oxygen in blood and tissue repair.

An interesting characteristic of iron is that it can be in *different oxidation states ranging* from +2 to +6. When iron is in a **lower oxidation state**, it is more easily absorbed by the body and used for biological functions.

In this article, we will discuss how to find the ground-*state electron configuration* of Fe3+, or how many unpaired electrons are present in one iron atom in its lowest oxidation state (+3).

## Determine which subshell has the most electrons

In order to determine how **many unpaired electrons** are in the *ground state electron configuration* of Fe3+, you must first determine which subshell it is in.

The 3d subshell has six electrons, so if Fe3+ is in the 3d subshell, it would have six paired electrons and **one unpaired electron**. This would make it Fe2+ instead of an ion with a +3 charge, so that is not correct.

The 4s subshell has two electrons, so if Fe3+ is in the 4s subshell, it would have two paired electrons and two unpaired electrons. This would make it Fe5+, which is not correct either.

The only other possible option is that Fe3+ is in the 3d orbital shell, which has six electrons. Five of these are paired, **leaving one unpaired electron**.

## Figure out how many electrons are in each orbit

Now that you know how to find the number of electrons in each orbit, you can figure out how many electrons are in each atom.

Atoms are made up of nuclei and orbits. Orbits are regions in which electrons can be found. There are **two fundamental properties** of orbits: width and energy.

The width of an orbit is simply how big it is. All orbits have the same width, which is why there is only one number for this property.

The energy of an orbit is how far up or down the spectrum of energies it is. This has to do with *gravitational force*, electromagnetism, and other forces that affect the orbital. There are **several numbers** that represent the different energies of an orbit.

To figure out how many electrons are in each atom, *first count* the number of protons in the nucleus, then subtract this number from Zowie! That was close!the atomic number and you will have the answer.

## Determine how many electrons are paired and unpaired

Now that you know how to determine the number of electrons in each orbital, you can determine how many are paired and unpaired.

When looking at the d-orbitals, there are five of them. Each one can *hold two electrons*, for a total of ten. When you factor in the 3s and 3p orbitals, which **also hold two electrons** each, you get a total of eighteen electrons.

Since there are only eighteen electrons in the neutral Fe3+ atom, all of its d-orbitals must be full. There are no unpaired electrons in this atom!

Now, let’s look at the ground-*state electron configuration* of Fe3+. How *many unpaired electrons* are present? The answer is none! All eighteen electrons in this atom are paired.

## Know that the 3s electron is lower in energy than any other 3p electron

In the case of iron, there is a configuration in which the atom has no unpaired electrons. In this case, all of the electrons are paired with other electrons, and there is no net electron charge.

The **ground state electron configuration** of iron is [Ar] 3d6 4s2 3p6. There are two reasons why this configuration is special.

The first reason is that there are no possible configurations with ** fewer total electron charges**. That is to say, there cannot be any configurations where there are fewer unpaired electrons.

The second reason is that all of the possible configurations with fewer total electron charges have higher energy than this one. This means that this configuration described is the most stable one!

Iron is an important element that we use every day. Did you know that 1 in **every 5 blood donations contains iron**? Learn more about iron here.

## Use a molecular orbital diagram to help you determine what is going on with your atoms and electrons

So now that you know how to find the number of unpaired electrons in a atom, let’s put that knowledge to good use!

Unpaired electrons can be found in **several different circumstances**. One of these is in a molecule, where the electron pairing is altered.

To see why this happens, you need to *understand molecular orbital diagrams*. These **diagrams show** the distribution of electron density (the place where the electrons are) among the atoms in a molecule.

By looking at the shape of these distributions, you can see which atoms are close to each other and which atoms are not. You can also tell which side of an atom the electron density is on- this tells you which direction the atom is spinning!

This is very useful information, and will help you determine how **many unpaired electrons** your molecule has.

## Remember that lower energy states are more stable than higher energy states

The answer to this question depends on how you look at the electron configuration of Fe3+.

If you consider only the 3d electrons, then there are five. There is one s-electron, two p-electrons, and two d-electrons. These are all paired up with other electrons, making them stable.

If you consider all of the electrons in the atom (including those in the 1s orbital), then there are seven. There is one s-electron, two p-electrons, and four d-electrons. These are all unpaired, making them unstable.

The difference between these answers is due to how we define what it means to be an electron. In general, **atoms try** to have as *many neutral atoms* as possible (i.e., having an equal number of positive and negative charges).

## Check your work using mathematical equations

Once you have determined the number of **unpaired electrons** in a atom, you can then determine the number of electrons in the molecule. You do this by adding up the numbers of electrons in each atom that makes up the molecule.

For example, in ferrous ion, Fe2+, there are two atoms of iron with **six valence electrons** each, so there are

*12 valence electrons total*. When you add an electron to make the neutral atom, there is one more valence electron, making a total of 13.

You can also check your work by calculating the net charge of the molecule. If your answer is correct, then you have done it correctly!

Unpaired electrons can sometimes be harder to detect due to their similar behavior to paired ones. Be sure to check your observations against other sources and others that have tested it before you.