Atomic theories

Democritus

each atom is different size weight and shape

Democritus (400 BC)

if you continued to divide a piece of atom you will eventually get something that could not be divided anymore he called these atoms

J.J. Thomson (1897)

- identified negatively charged particles (electrons)

Ernest Rutherford (1909 - 1911)

- hypothesized that all the mass of an atom was in the center

- the name proton was given to positively charged particles

- predicted that there was something else in the nucleus (aka neutrons(

Neils Bohr model (1913)

- electrons orbit the nucleus in orbits that have set size and energy

- as the electron gets farther away the energy of the electron increases

Louis de Broglie and Erwin Schrödinger

showed where electrons are most likely to be found in an atoms orbital

Law

describes what happens in a particular situation (no explanation)

Theory

explains WHY something happens

Law of Conservation of Mass

Matter is not created nor destroyed in any chemical or physical change

Law of Definite Composition

compounds always contain the same elements in a constant proportion by mass (water will always be 2 hydrogen atoms and 1 oxygen atom)

Dalton (1803)

- All matter is made of atoms

- atoms can't he created or destroyed

- all atoms of the same element are identical in mass and size

- compounds are created when different elements link together in define proportions