Bohr's Model of the Atom
- In 1913 the Danish Physicist, Niels Bohr, came up with an improved model of the atom
- He used the nuclear model to create his model
- In the Bohr model of the atom:
- Electrons orbit the nucleus at different distances
- The different orbit distances are called energy levels
- Up to 2 electrons orbit in the first energy level
- Up to 8 electrons can orbit in the second energy level
- Up to 8 electrons can orbit in the third energy level
In the Bohr model of the atom electrons orbit in distinct energy levels, which are at different distances from the nucleus
Successes of the Bohr Model
- The Bohr model became the accepted model because:
- It was able to explain the findings from different experiments better than the nuclear model of the atom
- It was able to explain the processes of absorption and emission of electromagnetic radiation
- Theoretical calculations made using the Bohr model agreed with experimental results
Worked example
The Bohr model of the atom replaced the nuclear model of the atom.Describe the main advantage of the Bohr model over the nuclear model.
Step 1: Describe the difference between the two models
- The nuclear model describes the atom as having a positively charged nucleus with electrons orbiting it
- The Bohr model is similar to the nuclear model in that it describes the atom as having a positively charged nucleus but the electrons orbit at specific distances in distinct energy levels
Step 2: Describe why the Bohr model was better
- The Bohr model could explain the findings of experiments better than the nuclear model
In my experience of teaching GCSE, the changing atomic model is a great lesson in which to discuss the scientific process, of which you are expected to know, but are never directly taught. In science, there are no absolute 'facts', there are just theories that have yet to be disproven. In science, we change our way of thinking based on evidence. Using the scientific method, we come up with theories based on observation, make predictions based on the new theory, then we test the prediction using experiments. If the experimental evidence doesn't fit the prediction, we change the theory.
The 'facts' we learn in science are our best understanding to date of how things work. However, these theories have been rigorously tested by many scientists many times, and those experiments have been peer-reviewed - meaning that a panel of scientists has assessed the validity of the results from the experiment. This scientific process ensures that we can be as certain as possible about our body of knowledge, whilst striving to learn new things.
