432 BCE- Empedocles
Empedocles was responsible for separating air as a separate substance. In his beliefs air, fire, water, earth mingle and separate under the compulsion of love and strife.
440 BCE- Democritus
Democritus’s theory was the first theory to be contributed to the atomic theory. He proposed that the entire world was made up of tiny particles surrounded by an empty space. He also said that they were invisible physically but not geometrically. He called these particles Atomos.
440 BCE- Aristotle
Aristotle’s contribution was completely different; he disagreed with Democritus and stated that particles comprise the four elements instead. And most scientists believed him over Democritus.
500 BCE- Alchemists
Alchemists developed the idea that all metals are composed of mercury & sulfur and that changing base metals into gold is possible.
1803- John Dalton
John Dalton’s contribution was that he reintroduced the idea of particles, which vary in shape and size based on the substance type and the mass and volume of this substance. He also showed that common substances always broke down into the same elements and the same proportion they were in previously.
1831- Michael Faraday
Faraday’s discoveries led to the idea that atoms had an electrical component. In his experiment, he placed two opposite electrons in a water solution containing a dissolved compound.
1897- J.J. Thomson
Thomson’s contribution was the discovery of the electron. He also created the Plum Pudding Model. He believed inside an atom were negative and positive particles mixed with a positive between each negative.
1911- Ernest Rutherford
Known as the father of the nuclear age. Rutherford discovered that atoms are mostly surrounded by an empty space, with just a few electrons, while most of the mass was in the center, which he termed the nucleus.
1913- Niels Bohr
Bohr’s contribution was expanding on Rutherford’s model and discovered that the electrons circle the nucleus at fixed energies and distances and can jump from one level to another but not exist in the space between.
1932- Sir James Chadwick
Chadwick was responsible for discovering the neutron in atoms. Neutrons are located at the center of an atom in the nucleus. They have neither a positive nor negative charge but the same weight as a proton.
1938- Lise Meitner
Meitner discovered that nuclear fission can produce enormous amounts of energy. She was discovered in Sweden after she escaped Nazi Germany. After World War 2 ended, she was named the mother of the atomic bomb.
1948- Maria Goeppert-Mayer
Goeppert-Mayer was responsible for presenting the nuclear shell model of the atomic nucleus. She was the second woman to receive the Nobel Prize for physics
