atomic theory timeline

Democritus(460-370 BC)

1st to propose atoms

Called them "atomos"

Greek for "uncuttable"

aka: The Laughing Philosopher

Aristotle(384-322 BC)

Didn't agree with Democritus' "atomos"

Said everything is made from 5 elements:

earth

water

air

fire

aether

John Dalton(1766-1844)

Formulated a concrete version of Atomic Theory

Submitted in 1808

Developed the Law of Multiple Proportions

Dalton's Atomic Theory

All matter is made of atoms. Atoms are indivisible and indestructible.

All atoms of a given element are identical in mass and properties.

Compounds are formed by a combination of two or more different kinds of atoms.

A chemical reaction is a rearrangement of atoms.Law of Conservation of Mass

Law of Definite Proportions

A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.

Law of Multiple Proportions

If two or more different compounds are composed of the same two elements, the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.

J.J. Thomson(1856-1940)

Discovered the 1st subatomic particle - THE ELECTRON!discovered in 1897

used a cathode ray tube

used a plum pudding model (or chocolate chip cookie)

Won the Nobel Prize in Physics in 1906

Thomson's Plum Pudding Model

Thomson's Plum Pudding Model

Robert Millikan(1868-1953)

Determined the charge on electrons to be negative

Discovered this in 1910

Used the oil drop experiment

Won the Nobel Prize in Physics in 1923

Millikan's Oil Drop

Ernest Rutherford(1871-1937)

Discovered the nucleus!

1911

Used the Gold Foil Experiment

Won the Nobel Prize in Chemistry in 1908 for his work in radioactivity

Neil's Bohr(1885-1962)

Said that electrons travel in "orbits" around the nucleus and that they can jump to higher/lower orbits

1913

Created Bohr Model of the Atom

Won the Nobel Prize in Physics in

Erwin Schrodinger(1887-1961)

Suggested the quantum mechanical model of the atom - probability of finding an electron in a certain location

1926

Won the Nobel Prize in Physics in 1933 for making the Schrodinger equation

James Chadwick(1856-1940)

Discovered neutrons

1932

Won the Nobel Prize in Physics in 1935