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400 BCE
Democritus
He proposed the idea of the atom as ‘indivisible and invisible’. However, he didn’t have any evidence, but based this on reason. This contributed to the atomic theory by being the central point/start of the atomic theory. -
John Dalton
His idea of atomic theory had 5 key points;
- all matter is composed of atoms
- atoms can’t be created or destroyed
- all atoms of the same element are identical
- chemical reactions occur when atoms are rearranged
- compounds are formed by the combination of 2 or more different kinds of atoms
In short, all matter is made of atoms and all atoms of an element are the same, but different elements atoms have different sizes and masses. And new substances can be made when you combine elements. -
J.J. Thompson
He came up of the idea of the electron. The electron is a negatively charged particle in an atom. He created the cathode ray tube. It would create a stream of electrons that were attracted to postitve charges. -
Neils Bohr
He discovered that electrons can only exist at certain energy levels and can’t exist between these energy levels. But they can be given enough energy to jump to the next energy level. He called these energy jumps ‘quantums’. -
Ernest Rutherford
He discovered the positively charged proton. He also ended up having to remodel the atom to the modern model of an atom. -
Loui De broglie
Waves can act like particles and particles can act like waves. He thought that electrons were better described as waves than particles. He also discovered that all particles have wave properties. -
Erwin Schrödinger
He created an equation that finds where the electrons are most likely to be located. This created the electron cloud model. -
James Chadwick
He discovered the neutron. This completed the model of the atom. -
The modern atom
All of these scientists research and discoveries lead to the atom being modeled accurately.
