May 31, 2020
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The history of the atomic model
⟶ Updated 15 Oct 2017 ⟶
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465 BC: A Greek philosopher, Democritus, also known as the father, of atomic thought came up of a theory in 465BC. He hypothesized that the universe is composed of two elements: the atoms and the void in which they exist and move. He deduced that all matter is made of an infinite amount of invisible atoms that vary in size, density, shape, and temperature.
1803 AD: John Dalton, a chemist and schoolteacher performed various experiments related to atoms such as mixing gases and explaining compounds. In 1803, he came up with the very first atomic theory: Atoms of the same element are identical, Atoms of different elements have different weights and chemical properties, compounds are formed when elements are combined and atoms cannot be created or destroyed. He also created the very first model of what an atom would look like.
1896 AD: Frederick Soddy, a radio-chemist who worked in nuclear chemistry studied the 1896 radioactivity phenomenon and he discovered after a chain of experiments that atoms could have the same chemical properties but can change those properties when it came to radioactivity. In 1913 Soddy claimed a new theory that atoms can have isotopes that change its weight.
1900 AD: Max Planck, a German physicist, famous for his work in thermodynamics, he announced that hot glowing matter radiates energy in small amounts or packets, not one continuous wave. This is known as Planck’s constant from 1900.
1897 AD: In 1897, J.J Thompson demonstrated that atoms were made up of even smaller particles called electrons, which gave the atom a (-) charge through electric field experiments. His model of an atom was known as a raisin bun model and was an improvement of Dalton’s model, with added electrons.
1911 AD: Following closely in 1911, a scientist, Earnest Rutherford designed an experiment that founded the protons and the nucleus. The protons had a (+) charge and was placed in the middle of the atom, called the nucleus and the electrons encircled the nucleus, the rest mostly being empty space. His model was named the Plum Pudding model.
1913 AD: Niels Bohr, a Danish physicist improved on Rutherford’s model, claiming that electrons moved in specific layers or shells and each shell could only have a certain number of electrons. His model was announced in 1913 and is known as the Bohr model.
1932 AD: James Chadwick, working with nuclear physics used alpha particles and discovered the neutron, the same mass as a proton and is found in the nucleus. They also had no charge and this model was a major improvement from Bohr’s model.
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