Atomic Models: Centuries ago, people didn’t know exactly what was inside an atom, but they had some “ideas”. Around 400 BC, a Greek philosopher named Democritus came up with a theory that everything in the world was made of tiny indestructible particles called “atomos”, which means “uncuttable”. However, this theory was largely discredited by Aristotle—the original social influencer, who believed that everything on this planet was made of four elements: earth, fire, water, and air.
The next step in atomic theory development didn’t happen for nearly 2000 years, when British chemist John Dalton conducted some experiments. Following his breakthrough, Dalton proposed that everything in the world was made up of atoms—tiny indestructible solid spheres that were unique for every element. Atoms of different elements combine to form different compounds and are rearranged during chemical reactions.
After that, came an English physicist named J.J Thompson and his trusty cathode ray tube. He proposed the famous “plum pudding” model. This model characterizes an atom as a particle that is composed of a positively charged mass (the pudding), as well as tiny negative charges embedded in it (like plums). After this, another chemist called Rutherford proposed his model of an atom where most of the atom’s mass was concentrated in a positively charged center (which he later named the nucleus) around which the electrons orbited like planets around the sun. After Rutherford, another chemist Neils Bohr theorized that if an electron jumped to a lower energy orbit, it would give out the extra energy in the form of radiation, thereby maintaining atomic stability. Even though Bohr’s model doesn’t hold true for complex multi-electron systems, this model is still the most popular representation of atomic structure in most textbooks.
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