History of the Atom by Cady Heard and Pacee Wallace

Democritus (492 BC)

450

Demcritus believed that an object had indivisible pieces of matter called an atom. He claimed that everything was made up of atoms, which were indivisible, always in motion, and had an infinite number, type, and size.
Democrtius based his findings observations.
*He did not know what an atom looked like. He only knew that an object could only be cut down to a certain size.

Aristotle (340)

500

Aristotle belived that the atom did not exist. He belived that everything was made up of tiny particles of water, earth, fire, and air.
He studied many different sciences to make his discovery.

Dalton

Feb 21, 1803

Dalton introduced a modern atomic theory that proposed elements differ due to the mass of their atoms. He also believed that all compounds of combinations of atoms in defined ratios.
He gathered evidence from experiments to make his discovery.

Thomson

Feb 21, 1897

Eh discovered the electron during an experiment using a vaccum to discover about electric discharges. His model is called the Plum-Pudding Model, which has the electron randomly stuck into a positive 'pudding' like substance.
Dalton made his discoveries by experimanting.

Rutherford

Feb 21, 1911

He discovered that the nucleus has a positive charge, and that the atome is made up of mostly empty space. He discovered this through the Gold Foilf Experiment in which he shot alpha particles at gold foil and watched to see where they ricocheted.His model is known as Rutherford's Model.
Rutherford gathered information from experiments to make his discoveries.

Bohr

Feb 21, 1912

He discovered that the electron orbiting the nucelouscan only ahve a ceratin amount of energies. His model was called the quantam shell model.

Heisenberg and Schrodinger( 1925 & 1926)

Feb 25, 1925

Heisenberg described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle.
Shroedinger introduced the Shroedinger Equation, a wave equation that describes the form of the probability waves that govern the motion of small particles and how these waves are altered by external influences.