Unit 3 Atoms

John Dalton

Theory: all matter is made up of atoms

Also thought that atoms cannot be created, divided, or destroyed

Also stated that all atoms of a certain element are identical, but different from any atom of any other element

J.J. Thompson

found that particles within the atom that have a negative charge

thought that atom was a positive sphere with electrons mixed through it

The negatively charged particles later became known as electrons

Ernest Rutherford

experiment stated that atoms have a nucleus, small, dense center that is positive and is surrounding by moving electrons

later found that nucleus is made up of smaller particles: called them protons

Niels Bohr

led to theory of how electrons in a atom behaved

agreed that an atom has a positive nucleus surrounded by electrons

helped scientists predict the chemical properties of elements

Atom: smallest particle into which an element can be divided ans still be the same element

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Democritus

Aristotle

eventually end up with a particle that could not be cut

Aristotle disagreed

called particles atomos

did not belive that such a particle could make up all substances found in nature