Chem Project

Heraclitus

500 BCE

He believed that everything was made out of fire.

Democritus

370 BCE

This philosopher believed that atoms were made of invisible particles. If you broke the atom down then eventually you would have to stop.

Aristotle

322 BCE

Aristotle believed that everything was made out of the four different elements, water, fire, earth, and air. Then other stuff was made from a blend of the elements.

Dalton

1803

1) All matter is composed of atoms
2) All atoms of a given element are identical in all properties
3) Atoms are cannot be broken down
4) Atoms of different elements combine in whole-number ratios to form chemical compounds
5) In chemical reactions atoms are combined, separated, or rearranged

Thomson

1856

He discover cathode rays and that led to the discovery of negatively charged particles also known as electrons. A cathode ray is a beam of electrons emitted by a a high voltage vacuum. Johnson also discovered plum pudding which is a model that has electrons and protons.

Rutherford

1871

Rutherford did an experiment with gold foil and assumed that the mass and charge would effect the atom and it would all go through the gold foil. However most of the atoms went through the foil but a few hit the atom. As a result this would tell us that the atom is mostly empty but there is weight in the nucleus. Rutherford's theory also supports Dalton's theory about atoms almost being invisible.

Bohr

1913

He discovered that electrons give off different colors of light. Every element has different placement of electrons so different colors would be given off. His discovery shows that the distance electrons move also determines the wavelength of light and the wavelengths have different colors.

Schrodinger

1926

Schrodinger's found that electrons don't orbit. He also found that electrons are outside of the cloud but we don't know where outside the nucleus the electrons are. Schrodinger's findings contradict what Bohr found about electrons orbiting.

Chadwick

1932

Chadwick discovered the neutron. He also found out the there was more mass in the nucleus that could not be taken up by protons. This lead to the discovery of the neutron in the nucleus. This adds to Schrodinger's idea that there is more in the nucleus.