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460 BCE
Democritus
The first person to propose "Atoms". He thought that everything was made up of small particles. He called them "Atomos" meaning unbreakable, as he says that that is the point that you cannot divide the substance anymore. He also said that atoms have no internal structure, there is an empty space between them and that each atom is different in size and weight. -
Dalton
He agrees that all matter was made by atoms, which he though were indestructible. He also stated that compounds were made by combining two or more atoms. -
Mendeleev
He created the periodic table of elements. He did this by grouping elements by their similarities, with a law that 'Physical and chemical of the elements are periodic functions of their atomic numbers, which means that each atom is different to each other. -
Eugene Goldstein
Goldstein discovered positive and negative particles. He also said that the particles had a charge equal and opposite to the electron. -
J.J. Thomson
He discovered the electron, and called it Corpuscles. He did this by studying the nature of electric discharge in a high vacuum cathode-ray tube. He also thought that only electrons were the many thing inside atoms, and famously made the plum pudding model. -
Ernest Rutherford
He fired positive charged alpha particles into a thin sheet of gold foil. This resulted in most passing through, but while some weren't deflected, others were. He then concluded that this was only possible if the atom is made up of mostly empty space, with the main positive charge in the middle, the nucleus. This made the Nuclear Model, a model that we all recognize to this day. -
Robert Andrews Millikan
He used the oil drop method to find out that electrons have a negative charge. -
Niels Bohr
Bohr modified Rutherford's model of the atom but saying that the electrons move around the nucleus in orbits of fixed sizes and energies. While this may be correct, the electrons, for heavier atoms, will just push in and collapse into the nucleus. -
Frederick Soddy
Came up with eh concept of isotopes. He also explained with Ernest Rutherford that the transmutation of elements cases radiation. -
Werner Karl Heinsberg
Came up with the Uncertainty Principle. This means that nobody will know the exact location and energy of an electron simultaneously. -
Erwin Schrödinger
He stated that electrons do not move in paths around the nucleus, but in waves. This means that we do not know the exact location of atoms, but instead we have clouds, which have a probability of having the electrons inside them. He called them orbitals. -
James Chadwick
Discovered the neutron, which is in the centre of the nucleus, and helps balance out protons in the nucleus of the atom.