# Calcium Bohr model

The calcium Bohr model includes a nucleus with 20 protons and 20 neutrons. Surrounding this nucleus are four electron shells, holding a total of 20 electrons.

To draw the calcium Bohr model, represent the 20 protons, 20 neutrons, and 20 electrons. Start by sketching the nucleus, and then illustrate the four electron shells. The first two shells should contain 2 and 8 electrons, respectively, while the third and fourth shells hold 8 and 2 electrons, respectively.

Contents

## Steps

### Write protons, neutrons, and electrons of calcium atom

Calcium has 20 protons, 20 neutrons, and 20 electrons.

### Draw nucleus of calcium atom

The nucleus of a calcium atom contains 20 protons and 20 neutrons. So draw the nucleus of calcium 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 20 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 20 – 2 = 18 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 20 – 10 = 10 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 and 3p subshells. And the green and orange color represents the number of electrons in that subshell. This means that the 3rd electron shell has a total of 8 electrons.

The 3rd electron shell contains only 3s and 3p subshells, and not a 3d subshell. This is because according to the aufbau principle, the 4s subshell is filled first and then 3d, 4p, 5s… and so on.

Now we have already used 18 electrons in 1st, 2nd, and 3rd electron shells, so we have 20 – 18 = 2 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 subshell. And the green color represents the number of electrons in that subshell. This means that the 4th electron shell has a total of 2 electrons.

That’s it! This is the final Bohr model of calcium atom as we have used all 20 electrons: 2 electrons in the 1st electron shell, 8 electrons in the 2nd electron shell, 8 electrons in the 3rd electron shell, and 2 electrons in the 4th electron shell.

Next: Rubidium Bohr model