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Period: 460 BCE to 370 BCE
Democritus
His atomic theory was that everything was created of tiny atoms. He also believed that atoms were indestructible. Different shapes of atoms give them different properties. Changes were seen are caused by the movement. -
Period: to
Dalton
His atomic theory that elements are made of extremely small particles called atoms. He also believed that atoms of a given element are identical size, mass and other properties, atoms of different elements differ in size, mass and other properties. Atoms can be subdivided, created or destroyed. -
Period: to
Thomson
In 1897, Thomson showed that cathode rays were composed of previously unknown negatively charged particles, which he calculated must have bodies much smaller than atoms and a very large value for their charge-to-mass ratio. -
Period: to
Rutherford
His atomic theory suggested that positive chargers of the atom were found mostly in the centre, in the nucleus and the electrons around it. -
Period: to
Bohr
In quantum mechanics, a branch of physics, the Bohr model is the model of the atom proposed by Niels Bohr. Bohr's model is useful only when discussing the behavior of a hydrogen atom. Bohr's model is extremely useful in describing the hydrogen emission spectrum.