History of the Atom

Democritus - 400 BC

If you keep cutting a substance to where you can’t cut anymore that is an atomos

Aristotle - 350 BC

Matter is made of fire, earth, water, and air.

John Dalton - 1803

He revived Democritus’s theory and made the “Billiard Ball Model”

J.J. Thompson - 1904

Created the “Plum Pudding Model.” The plums are the positive charges and the pudding is the electrons spread out

How did J.J. Thompson test out if electrons were real

He experimented with electric currents in his cathode ray tube. He made non-radioactive atoms produce negatively charged particles. Electrons.

Ernest Rutherford - 1911

The centre of the atom is positively charged (nucleus) and the electrons surround it.

What experiment proved that there was a nucleus

The gold foil experiment. He shot positively charged particles at gold foil and some of them bounced back.

Neil’s Bohr - 1913

In his model the electrons are arranged in the way we do it today (2 first row, 8 on the rest)

James Chadwick - 1932

Discovered the neutron

How are protons different from electrons

Location

Mass

Symbol