History of Atomic TheoryResearch the discoveries and experiments of scientists and their contribution to “atomic theory”

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Democritus & DaltonDemocritus (460 BC)

First to develop the idea that matter was made of “atoms”.

Dalton (1803)

Proposed the atomic theory

atoms are indivisible & indestructible

elements have unique atomic masses

Mendeleev (1869)

Developed the first basic periodic table

Table was arranged by atomic weight

was able to predict elements which hadn’t been found

J.J. Thomson (1898)

• Discovered electrons (-e)• Atoms have — & + charges

Rutherford (1911)

Discovered the positively charged nucleus

shot positively charged particles through gold foil

electrons moved in circles

Bohr (1913)

Electrons move in specific energy levels (orbits) around the nucleus

Schrodinger (1926)

Described electrons as waves

Electron cloud

Chadwick (1932)

Neutrons (and protons) made

up the nucleus

Evolution of the

Atom

Evolution of the Atom