This is a schematic representation of an atom. The nucleus is comprised of equal number of protons and neutrons. The electrons orbit in very distant orbits around the nucleus (the electron orbits are not to scale)
In 1913, the Danish physicist Niels Bohr developed a different atomic model, which departed slightly from the Rutherford model. It in fact adds consideration of quantum physical calculations to the Rutherford model. Many sources actually combine the two, referring to the Rutherford-Bohr model. The Bohr model is essentially a primitive model of the hydrogen atom, and by today’s standards an obsolete scientific theory, which has been largely replaced by the more complex valence shell atom model. However, due to its simplicity and its correct mathematical calculations for selected systems, it lends itself as an ideal model to explain the generation of laser light.
We are surrounded by matter. It comes in various shapes and states. Our daily experience suggests that we can break any type of matter into smaller and smaller pieces. This subdivision of matter into successively smaller pieces (the practical and mechanical difficulties of such an endeavour set aside) will eventually come to a halt at the level of molecules. The molecular level sets the limit on mechanical breakdown of matter. If we were to break down the individual molecules of matter, we would have to apply either chemical or physical means. Once individual molecules are broken down further, we will eventually arrive at the atom, which is the smallest complete building block of matter.
Between the discoveries of J.J. Thompson in 1897, Ernest Rutherford in 1907 and James Chadwick in 1932, it came to be accepted that even atoms are composed of even smaller particles. These particles were in particular the electrons, and the protons and neutrons, which form the atomic nucleus. The electrons orbit the nucleus at a very great distance (relative to the atomic scale). Once it was discovered that the numbers of the protons, neutrons and electrons are related to each other, this relationship was utilized in the organization of the periodic table. The number of protons in the nucleus determines the actual element.
The Atomic Model
