# How many valence electrons does chromium(Cr) have?

The 24th element in the periodic table is chromium. The element of group-6 is a chromium and its symbol is ‘Cr’. Chromium is a transition element. Therefore, the valence electrons of chromium are determined differently.

The last shell(orbit) of a chromium element has only one electron but its valence electrons are not one. This article discusses in detail the valence electrons of chromium. Hopefully, after reading this article you will know in detail about the valence electrons of chromium(Cr).

## How many electrons and protons does chromium(Cr) have?

The nucleus is located in the center of the atom. Protons and neutrons are located in the nucleus. The atomic number of chromium is 24. The atomic number is the number of protons.

That is, the number of protons in chromium(Cr) is twenty-four. Electrons equal to protons are located in a circular shell outside the nucleus. That is, a chromium atom has a total of twenty-four electrons.

## What are the valence electrons of chromium(Cr)?

The 1st element in group-6 is chromium and this is the d-block element. The elements in groups 3-12 are called transition elements. The valence electron is the total number of electrons in the last orbit.

But in the case of transition elements, the valence electrons remain in the inner shell(orbit). This is because the electron configuration of the transition elements shows that the last electrons enter the d-orbital.

The electron configuration of chromium shows that the last shell(orbit) of chromium has a total of one electron. But the electron configuration of chromium in the Aufbau method shows that its last electrons(3d5) has entered the d-orbital.

The valence electrons determine the properties of the element and participate in the formation of bonds. The electrons of the d-orbital participate in the formation of bonds. So, To determine the valence electron of a transition element, the last shell(orbit) electrons have to be calculated with the d-orbital electrons.

That is, we can easily say that chromium has six valence electrons. There is an article on this site detailing the electron configuration of chromium(Cr), you can read it if you want.

## How to determine the valence electron of chromium(Cr)?

Now we will know how to easily determine the valence electron of chromium. The valence electron has to be determined by following a few steps. The electron configuration is one of them.

It is not possible to determine the valence electron without electron configuration. Knowing the electron configuration in the right way, it is very easy to determine the valence electrons of all the elements.

There is an article published on this site detailing the electron configuration, you can read it if you want. The valence electrons of the transition element cannot be determined according to Bohr’s atomic model. This is because the valence electrons of the transition elements are located in the inner shell(orbit).

The German physicist Aufbau first proposed an idea of electron configuration through sub-orbits. The Aufbau method is to do electron configuration through the sub-energy level.

These sub-orbitals are expressed by ‘l’. The Aufbau principle is that the electrons present in the atom will first complete the lowest energy orbital and then gradually continue to complete the higher energy orbital. These orbitals are named s, p, d, f. The electron holding capacity of these orbitals is s = 2, p = 6, d = 10 and f = 14.

However, the valence electron of the transition element can be easily determined according to the Aufbau principle. Now we will learn how to determine the valence electron of chromium(Cr).

### Step-1: Determining the total number of electrons

1st we need to know the total number of electrons in the chromium(Cr) atom. To know the number of electrons, you need to know the number of protons in chromium. And to know the number of protons, you need to know the atomic number of the chromium element.

To know the atomic number we need to take the help of a periodic table. It is necessary to know the atomic number of chromium elements from the periodic table. The atomic number is the number of protons. And electrons equal to protons are located outside the nucleus.

That is, we can finally say that there are electrons equal to the atomic number in the chromium atom. From the periodic table, we see that the atomic number of chromium(Cr) is 24. That is, the chromium atom has a total of twenty-four electrons.

### Step-2: Need to do electron configuration

Step 2 is very important. In this step, the electrons of chromium(Cr) have to be arranged. We know that chromium atoms have a total of twenty-four electrons. The electron configuration of chromium shows that there are two electrons in the K shell, eight in the L shell, thirteen in the M shell, and one in the N shell(orbit).

That is, the first shell of chromium has two electrons, the second shell has eight electrons, the 3rd shell has thirteen electrons and the 4th shell(last orbit) has one electron. The number of electrons per shell of chromium(Cr) is 2, 8, 13, 1. The electron configuration of chromium through the sub-orbit is 1s2 2s2 2p6 3s2 3p6 4s1 3d5.

### Step-3: Determining the valence shell(orbit) and calculate total electrons

The third step is to diagnose the valence shell(orbit). The last shell after the electron configuration is called the valence shell(orbit). The total number of electrons in a valence shell is called a valence electron.

But the valence electrons of the transition elements are located in the inner orbit(shell). For the transition element, the valence electron has to be determined by adding the total electron of the d-orbital to the electron in the last orbit of the atom.

The electron configuration of chromium shows that the last shell of chromium has one(4s1) electron and the d-orbital has a total of five electrons(3d5). Therefore, the valence electrons of chromium(Cr) are six. In this way, the valence electrons of all the transition elements can be determined.

## How to determine the valency of chromium?

The ability of one atom of an element to join another atom during the formation of a molecule is called valency(valence). There are some rules for diagnosing valency. The number of electrons in an unpaired state in the last orbital after the electron configuration of an atom is called the valency of that element.

The oxidation states of chromium(Cr) depend on the bond formation. The oxidation states of chromium are +2, +3, +6.

Also, valency is determined from the electron configuration of the element in the excited state. The electron configuration of chromium excited state is Cr*(24) = 1s2 2s2 2p6 3s2 3p6 4s1 3dx2 3dy2 3dz1.

Here, The electron configuration of chromium(Cr) shows that its last shell has two unpaired (4s1 3dz1) electrons. Therefore, the valency of chromium is 2. The valency depends on the bond formation. Chromium 2 and 3 valency’s are used most of the time.

## How many valence electrons does chromium ion(Cr2+, Cr3+) have?

The electron configuration of chromium shows that the last shell of chromium has one(4s1) electron and the d-orbital has a total of five electrons. There are two types of chromium ions. The ionic state of the element changes depending on the bond formation. Cr2+ and Cr3+ ions exhibit more than chromium atoms.

Cr – 2e → Cr2+

Here, The electron configuration of chromium ion(Cr2+) is 1s2 2s2 2p6 3s2 3p6 3d4. The electron configuration of chromium ion shows that chromium ion(Cr2+) has three shells and that shell has twelve electrons (3s2 3p6 3d4). For this, chromium ion(Cr2+) have a total of twelve valence electrons.

Cr – 3e → Cr3+

On the other hand, The electron configuration of chromium ion(Cr3+) is 1s2 2s2 2p6 3s2 3p6 3d3. The electron configuration of chromium ion(Cr3+) shows that chromium ion has three shells and that shell has eleven electrons (3s2 3p6 3d3). Here, the valence electrons of the chromium ion(Cr3+) are eleven.

## Compound formation of chromium

Chromium participates in the formation of bonds through its valence electrons. We know that the valence electrons in chromium are six. This valence electron participates in the formation of bonds with atoms of other elements.

The electron configuration of chlorine shows that the valence electrons of chlorine are seven. The chromium atom donates its valence electrons to the chlorine atom and the chlorine atom receives those electrons.

As a result, chlorine acquires the electron configuration of argon. Chromium(III) chloride(CrCl3) is formed by the exchange of electrons between one atom of chromium and three atoms of chlorine. Chromium(III) chloride(CrCl3) is ionic bonding.