# Cesium Bohr model

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The cesium Bohr model includes a nucleus with 55 protons and 78 neutrons. Encircling this nucleus are six electron shells, carrying a total of 55 electrons.

To draw the cesium Bohr model, outline the 55 protons, 78 neutrons, and 55 electrons. Begin by illustrating the nucleus, and then depict the six electron shells. The first five shells should contain 2, 8, 18, 18, and 8 electrons, respectively, while the sixth shell holds the remaining electron.

Contents

## Steps

### Find protons, neutrons, and electrons of cesium atom

Cesium has 55 protons, 78 neutrons, and 55 electrons.

#### Cesium protons

• Protons = atomic number

From the periodic table, find the atomic number of cesium.

The atomic number of cesium is 55. Hence, cesium has a total of 55 protons.

#### Cesium neutrons

• Neutrons = atomic mass – atomic number

The atomic mass of cesium is 132.90545, so we’ll take the roundup value as 133. And the atomic number of cesium is 55.

Subtract the atomic number (55) from the atomic mass (133). Hence, cesium has a total of 133 – 55 = 78 neutrons.

#### Cesium electrons

• Electrons = atomic number

The atomic number of cesium is 55. Hence, cesium has a total of 55 electrons.

### Draw nucleus of cesium atom

The nucleus of a cesium atom contains 55 protons and 78 neutrons. So draw the nucleus of cesium atom as follows:

Now in the next step, draw the 1st electron shell and start marking electrons.

### Draw 1st electron shell

Remember that we have a total of 55 electrons.

The 1st electron shell (containing s subshell) can hold up to a maximum of 2 electrons. So draw the 1st electron shell as follows:

In the above image, 1 represents the 1st electron shell that contains 1s subshell. And the green color represents the number of electrons in that subshell. This means that the 1st electron shell has a total of 2 electrons.

Since we have already used 2 electrons in the 1st electron shell, now we have 55 – 2 = 53 electrons left. So in the next step, we have to draw the 2nd electron shell.

### Draw 2nd electron shell

The 2nd electron shell (containing s subshell and p subshell) can hold up to a maximum of 8 electrons. So draw the 2nd electron shell as follows:

In the above image, 2 represents the 2nd electron shell that contains 2s and 2p subshells. And the green and orange color represents the number of electrons in that subshell. This means that the 2nd electron shell has a total of 8 electrons.

Now we have already used 10 electrons in 1st and 2nd electron shells, so we have 55 – 10 = 45 electrons left. So in the next step, we have to draw the 3rd electron shell.

### Draw 3rd electron shell

The 3rd electron shell (containing s subshell, p subshell, and d subshell) can hold up to a maximum of 18 electrons. So draw the 3rd electron shell as follows:

In the above image, 3 represents the 3rd electron shell that contains 3s, 3p, and 3d subshells. And the green, orange, and pink color represents the number of electrons in that subshell. This means that the 3rd electron shell has a total of 18 electrons.

Now we have already used 28 electrons in 1st, 2nd, and 3rd electron shells, so we have 55 – 28 = 27 electrons left. So in the next step, we have to draw the 4th electron shell.

### Draw 4th electron shell

The 4th electron shell (containing s subshell, p subshell, d subshell, and f subshell) can hold up to a maximum of 32 electrons. So draw the 4th electron shell as follows:

In the above image, 4 represents the 4th electron shell that contains 4s, 4p, and 4d subshells. And the green, orange, and pink color represents the number of electrons in that subshell. This means that the 4th electron shell has a total of 18 electrons.

The 4th electron shell contains only 4s, 4p, and 4d subshells, and not a 4f subshell. This is because according to the aufbau principle, the 5s subshell is filled first and then 4d, 5p, 6s… and so on.

Now we have already used 46 electrons in 1st, 2nd, 3rd, and 4th electron shells, so we have 55 – 46 = 9 electrons left. So in the next step, we have to draw the 5th electron shell.

### Draw 5th electron shell

The 5th electron shell can hold up to a maximum of 50 electrons. So draw the 5th electron shell as follows:

In the above image, 5 represents the 5th electron shell that contains 5s and 5p subshells. And the green and orange color represents the number of electrons in that subshell. This means that the 5th electron shell has a total of 8 electrons.

The 5th electron shell contains only 5s and 5p subshells, and not 5d and 5f subshells. This is because according to the aufbau principle, the 6s subshell is filled first and then 4f, 5d, 6p… and so on.

Now we have already used 54 electrons in 1st, 2nd, 3rd, 4th, and 5th electron shells, so we have 55 – 54 = 1 electron left. So in the next step, we have to draw the 6th electron shell.

### Draw 6th electron shell

The 6th electron shell can hold up to a maximum of 72 electrons. So draw the 6th electron shell as follows:

In the above image, 6 represents the 6th electron shell that contains 6s subshell. And the green color represents the number of electrons in that subshell. This means that the 6th electron shell has a total of 1 electron.

That’s it! This is the final Bohr model of cesium atom as we have used all 55 electrons: 2 electrons in the 1st electron shell, 8 electrons in the 2nd electron shell, 18 electrons in the 3rd electron shell, 18 electrons in the 4th electron shell, 8 electrons in the 5th electron shell, and 1 electron in the 6th electron shell.

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