Chapter I

In 1913, Neil Bohr published an article in The Philosophical Magazine regarding Ernest Rutherford's model and classical physics.

Bohr's model, sometimes called the planetary model, postulated that electrons revolves the nucleus, which contains protons and neutrons, on particular orbits of fixed the energy levels.

The electrons release energy in the form of photons to form electromagnetic radiation and jump to the lower energy orbit. The lowest level is called the ground level.

After the model was published, it leads scientists to start the study of spectral lines with hydrogen molecules. The scientists figured out that different element release EM waves of unique wavelengths, which lead to the concept of emission lines and absorption lines.

This model is more advanced than Rutherford's model as it gives more detail about the motion of electrons. In Rutherford's model, it states that an atom consists a positively charge nucleus where mass concentrated, and the light, negatively charged electrons revolves around. Bohr thought that is unstable, and proposed that the electrons will travel on fixed energy levels.