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340
Aristotle's contribution
340 BC. Aristotle did not agree with democritus' atomic model saying that everything was made up of fire, water, earth, air and aether. He said that fire, water, earth and air made up earthly things and that aether made up space and the heavens, -
350
Democritus' contribution
350 BC Democritus was most probably one of the first people to create an atomic model. It was very similar to our modern day one, Differences were that all atoms are either solids liquids or oils. Solids were made up of small pointy atoms. Liquids were made up of large, round atoms. Oils are made of very fine, small atoms that can easily slip past each other. He also thought atoms were invisible -
Period: 360 to
The timeline of the atomic model
It has had many changes throughout the years, this is the timeline of all of those changes. -
John Dalton's contribution
Dalton's theory was similar to democritus'. He created 5 famous laws that we still follow today. All matter consists of atoms. Atoms are indestrcuctible. Elements are characterised by the mass of their atoms. Atoms combine in whole number ratios. In a chemical reaction no atoms are destroyed or created. -
J.J Thomson's contribution
J.J Thomson first discovered the electron by experimenting. He won the nobel prize for his plum pudding model, however, this only showed negative electrons floating in a "soup" of positive charge, There was not any idea of a nucleus yet. -
Ernest Rutherford's contribution
Ernest Rutherford carried out some experiments which led to a change in ideas around the atom. His new model described atoms as a nucleus surrounded by electrons with protons inside it. The atom was also thought to be like a mini solar system where the electrons orbit the nucleus like planets orbiting around the sun. -
Niels Bohr's contribution
Niels Bohr patched up a few of the problems with Rutherford's model. For example, atoms only emitted light at certain frequencies which led Bohr to theorise that atoms could only orbit the nucleus in different energy levels or as we call them today, shells. -
James Chadwick's contribution
In 1920 Ernest Rutherford also predicted there must be another type of particle in the nucleus to balance out the protons. To make sure that the atom stays neutral, this particle would have to be neutral itself thus discovering neutrons. In 1932 James Chadwick discovered the neutron and measured its mass. This leads to our current atomic model that we still use today, the Bohr model with neutrons.
