Electron Cloud Model simplified

In this depiction we see a spinning fan. Can you see the blades? Can you tell their location at a given time? Not clearly right?  The electron cloud model works in a similar way. The blades being the electrons. 


Bohr talked about the electrons orbiting the atom's nucleus in a similar way planets orbiting the sun. Bohr's model is useful to understand the properties of the elements and their chemical interactions. However, it doesn't explain a lot of theories including the Stark effect, Zeeman effect and the behaviour of electrons except for the simplest types of atoms such as Hydrogen.

The Electron Cloud

The electron cloud model also known as quantum mechanical model was developed in 1925 by Erwin SchrÖdinger and Werner Heisenberg. This is one of the newer models of the atom. He used mathematics to claim that it is impossible to know for certain where an electron is at any given time. This is similar to the Heisenberg uncertainty principal.

How Does It Look Like?

It consists of a positively charges nucleus surrounded by a spherical space.

This is how the electron cloud model of the helium atom looks like. At the centre are two protons and two neutrons. Surrounding the nucleus is an electron cloud which cover the nucleus in all 3 dimensions.

You might notice that the coloured differently. It is darkest near to the nucleus and gets lighter as we travel away. This colour gradient is based on electron probability: The likelihood of finding an electron in a certain location. Hence we can say that is is more likely to find an electron close to the nucleus and the probability of its location decreases as we more further away.

Electron movement around the nucleus takes on the appearance of a cloud, and wherever the cloud is densest is where there is the highest probability of finding an electron.

 Difference b/w Bohr and Schrodinger's Models

Bohr: He assumed that the electron is also a particle.

SchrÖdinger: He assumed that the electron is a wave.

Bohr: He said that the nucleus was orbited by electrons.

SchrÖdinger: He said that the nucleus was surrounded by a cloud of electrons.

Basically Bohr said that the electrons orbited the nucleus in specified shell/orbit/energy level whereas SchrÖdinger said that the location of electrons was all based on probability.