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Aristotle's Theory of Matter (340 B.C.E.)
He believed that there were only four elements: air which was dry, earth which was cool and heavy, water which was wet and fire which was hot. Aristotle believed that all matter was made up either of one of the elements of water air earth and fire or combinations of these four elements. -
Indivisible, Solid Sphere Model
The Solid Sphere Model was the first atomic model and was developed by John Dalton in 1808. He hypothesised that an atom is a solid sphere that could not be divided into smaller particles. He came up with his theory as a result of his research into gases. He realised that certain gases only combined in specific proportions. -
Plum Pudding Model
J.J. Thomson came up with the plum pudding model in 1904. He envisioned that atoms consisted of fluid that was positively charged with negatively charged electrons floating in the fluid. Using a cathode ray tube, Thomson experimented with the electric and magnetic fields finding that they affected the position of the rays. He reasoned that the electric current was made of small particles, which he called corpuscles. Thomson later reasoned that "corpuscles" must come from the atom itself. -
Rutherford's Nuclear Model
Ernest Rutherford came up with the Nuclear Model in 1911. In an experiment where he took foil and fired alpha particles at it, he measured the deflection of the particles. He found that some particles weren't deflected at all, while others were sometimes deflected at large angles and some particles bounced back. He deduced that the foil wasn't made up of empty space, but instead had small clumps of matter. This made him realise that there must be something positively charged inside an atom. -
Planetary/Solar System Model
Niels Bohr came up the Solar system model of the atom in 1913. He realised that electrons traveled in separate orbits around the nucleus and certain colours of light were given off when elements were exposed fire. He believed electrons orbited the nucleus at different distances and determined that the electrons had different energies. The colour of the light depended on the energies of the orbits. It’s called the solar system model because the electrons that orbit the nucleus are like planets. -
Electron Cloud Model
A German scientist named Werner Heisenberg proposed the idea of the electron cloud model in 1927. It is the most recent model of the atom. Notice that instead of showing the paths of the orbit of the electrons it just shows a "cloud" around the nucleus. The cloud represents where any one electron could be at any time. This electron cloud model is based on quantum mechanics. -
Quark Model of the Atom
Quarks were discovered by Murray Gell-Mann in 1970. A quark is a fast moving point of energy and all protons and neutrons have 3. There are 2 types of quarks in neutrons and protons, up and down. Up quarks have a positive charge of 2/3 and down quarks have a negative charge of 1/3. The charge of the quarks makes up the electrical charge of the nucleus. Protons contain 2 up quarks and 1 down quark, while neutrons contain 2 down quarks and 1 up quark. This makes neutrons have its negative charge.
