Development of the atom

Who was the first person to discover the atom?

Democritus (5th century BC)

In 1804 who agreed with Democritus?

John Dalton, matter was made up of tiny spheres that couldn't be broken up - each element was made up of a different type of atom

What did JJ Thomson discover?

electrons

When did J.J. Thomson discover the electron?

1897

What kind of model did JJ Thomson suggest?

atoms were spheres of positive with tiny negative electrons stuck in them (plum pudding model)

When did Rutherford attempt the alpha scattering experiment?

1909

What did Rutherford discover?

Nucleus (gold foil) and protons (after Neils Bohr)

What is the alpha scattering experiment?

Rutherford set up an experiment where he fired a beam of positive alpha particles towards some thin gold foil. He found most of the particles went straight through the foil. This suggested that there was lots of empty space, however he noticed that some alpha particles were deflected, with a few by more than 90 degrees. = concentrated positive nucleus in the centre of the atom since two positive forces repel.

What was Rutherfords nuclear model?

A compact nucleus (fully positive) with a cloud of negative charge - the atom should collapse

When did Niels Bohr make his discovery?

1913

What did Niels Bohr discover?

Electrons orbit the nucleus, held in shells = prevents the atom from collapsing

What did James Chadwick discover?

Neutrons in the nucleus