The planetary model of the atom

The planetary model of the atom

At the beginning of the 20th century, 

a new field of study known as 

                                quantum mechanics 

emerged. One of the founders of this field was Danish physicist Niels Bohr,

                          who was interested in explaining 

                              the discrete line spectrum 

                         observed when light was emitted 

                                by different elements. 

 Bohr was also interested in the structure of the atom, which was a topic of much debate at the time. Numerous models of the atom had been postulated based on experimental results including the discovery of the electron by J. J. Thomson and the discovery of the nucleus by Ernest Rutherford. Bohr supported the planetary model, in which electrons revolved around a positively charged nucleus like the rings around

However, scientists still had many unanswered questions:$$

• Where are the electrons, and what are they doing?
• If the electrons are orbiting the nucleus, why don’t they fall into the nucleus as predicted by classical physics?
  

  According to classical physics, a negatively charged electron moving around in the positive electric field created by the nucleus should emit electromagnetic energy. The electron would continue to lose energy as it orbited the nucleus until it eventually collapsed into the nucleus. Unfortunately, this reasoning would suggest that all atoms are inherently unstable!
• How is the internal structure of the atom related to the discrete emission lines produced by excited elements?
  Bohr addressed these questions using a seemingly simple assumption: what if some aspects of atomic structure, such as electron orbits and energies, could only take on certain values?