Bohr Model

The Bohr model is the diagram we use today to visualize what an atom looks like.

click to enlarge

Orbitals: the space occupied by electrons, also known as shells

This is what Bohr believed:

• Electrons have certain energy levels
• When electrons jump to a different orbital, they release a certain spectrum of light
• Ground states are the lowest energy states
• Excited states are when the electrons jump into a higher or lower level
• Each element gives off a certain spectrum of light when they are heated

We use this to identify what elements are present in distant stars

 

Structure of a Bohr model

Here are the orders of the shells and the maximum electrons they can have

1^st shell: 2 electrons

2^nd shell: 8 electrons             } octet rule

3^rd shell: 8 electrons             }

In the middle of the diagram, we write the atomic number (number of protons) and the number of neutrons

For example:

The atomic number of chlorine is 17. The atomic mass of chlorine is ~35.

To find the number of neutrons we subtract the atomic number from the atomic mass

  35

­-17

 18

So in the middle of the diagram, we write

17p

18n