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First proposed that everything is made by tiny particals surrounded by empty space. he called these particles atomos Greek for indivisible. But other philosophers of his time disagreed especially Aristotle -
Aristotle disagreed with Democritus and believed that everything was made up of elements like water earth fire and wind -
Dalton thought that all substances if brocken down will have the same elements that have the same proportions. He believed that various compounds were combination of atoms of different elements. -
He made the discovery of the electron. He showed atoms as uniformly packed spheres of positive matter , filled with negatively charged electrons. -
He is known as the Father of nuclear age. He investigated atoms by shooting small positively charged alpha particles at a sheet of gold foil. The atoms thinly dispersed positive charge would not be enough to deflect the particles in anyone way. He concluded that atoms consisted largely l of empty space with just a few electrons and most of the mass was in the center the nuclues. -
He used the work of Albert Einstein and Max Planck. He discovered that the electrons orbited the nucleus, at the same energy and distances. It was later discovered that electrons behaved like waves. -
He showed that it was impossible to determine the speed and position of electrons. He made a Quantum model.