Today's model of the atom looks different from the models that came before it. Why has the model of the atom changed?

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In general, the model of the atom changed as technology advanced and allowed closer observations, and different types of experiments. The ancient Greeks theorized about matter being made of small particles. In 1803 John Dalton proposed the first real atomic theory, which consists of four parts:

1) All matter is made of atoms. Atoms are indivisible and indestructible.

2) All atoms of a given element are identical in mass and properties

3) Compounds are formed by a combination of two or more different kinds of atoms.

4) A chemical reaction is a rearrangement of atoms.

Michael Faraday, using electrodes, theorized that electrical forces held atoms together. Use of cathode ray tubes further refined atomic theory through discovery of basic structure with electrons orbiting a nucleus of protons and neutrons. The discovery of radioactivity allowed study of the energy involved in atomic change. Particle accelerators have helped to lead to the discovery of even more elusive component pieces,such as quarks, leptons, and bosons.

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