Why did Bohr propose a new atomic model?

Bohr proposed a new atomic model to explain the stability of atoms and the emission and absorption spectra of hydrogen.

Niels Bohr, a Danish physicist, proposed a new atomic model in 1913. This was necessary because the existing atomic model, proposed by J.J. Thomson, could not explain certain phenomena. Thomson's 'plum pudding' model suggested that electrons were scattered throughout an atom like plums in a pudding. However, this model could not explain why atoms were stable and why they emitted or absorbed light in a specific way.

Bohr's model, often referred to as the Bohr model, proposed that electrons move in fixed orbits around the nucleus, similar to planets orbiting the sun. This was a significant departure from the 'plum pudding' model. Bohr suggested that electrons could only occupy certain energy levels, and could move between these levels by absorbing or emitting energy. This energy is observed as light, and the specific energy levels of the electrons explain the unique emission and absorption spectra of each element.

Bohr's model was particularly successful in explaining the behaviour of the hydrogen atom, the simplest atom with only one electron. The model could accurately predict the frequencies of light emitted by hydrogen, something the 'plum pudding' model could not do. This was a major breakthrough in atomic theory and marked the beginning of quantum mechanics.

However, it's important to note that while Bohr's model was a significant improvement, it was not perfect. It worked well for hydrogen but was less successful for larger atoms. Despite its limitations, Bohr's model was a crucial step in the development of modern atomic theory, paving the way for the quantum mechanical model we use today.