History of the Atom Timeline by Autumn Jones

Aristotle B.C.

350

DISCOVERY:
-atoms didn't exist
-said that atoms would fall down like rocks
-believed that everything was made from either dryness, wetness, heat, and coolness
METHOD:
-didn't agree with Democritus, so he came up with an idea that everything was made up of dryness, wetness, heat, or coolness.

Democritus B.C.

460

If he were to break a half a piece of matter until it can't be broken anymore, he would find the smallest thing on Earth. Once he found it, he called it the atom. He said that if an object is hard then the atoms are far apart. Atoms can't be destroyed and they can't change.
METHOD:
-thinking how things are made
-Thought that if he were to break up a piece of matter until it can't be broken anymore, he would get an atom
-He did all of this because of his reasoning.

Dalton

Feb 28, 1803

Discovery:
-everything was made from atoms
-said that atoms can't be created of destroyed
-arranged in diff. combination to make diff. compounds
-tiny, invisible
METHOD:
-conducted the first scientific experiment and imagined what they looked like

Thomson

Feb 28, 1897

Discovery:
-discovered that electrons are much smaller then atoms
-says atoms aren't invisible b/c they're made up of electrons
Methods:
-imagine like a blueberry muffin
-when split in half, there would be electrons stuck in it like blueberries in a muffin
-the dough would be positively charged
-the negative and posotive would balance eachother out making it a neutral atom

Rutherford

Feb 28, 1911

Discovery:
-found out that the electrons oribited aroudn the nucleus
-said that the center of an atom is posotively charged
-said the atom will collapse as the electrons orbit around the nucleus
METHODS:
-observed a particle go's around an atom & saw it weakly bounced off of something dense.
-concluded that the thing the particle hit was the center of an atom & called it the nucleus
-used gold foil, beam of alpha particles & a screen to see if the particles bounced off the gold or went through

Bohr

Feb 28, 1913

Duscovered:
-electrons orbit in a fixed path
Method:
-observed Rutherford's model of the atom & added electrons in electron shells
-used spectrum of light to discover that electrons are in fix paths
-saw that electrons give off light when they change direction and used this info to announce hit theory

Heisenber & Schrodinger

Mar 6, 1926

Discovery:
-Electrons are waves and orbit the nucleus
Methods:
-Use the "two-slit experiment" This is when you send out info. & the info is carried, there is a wave.
-He sent out the info., sound, to the electron & saw that it can carry the sound
-this made him find out that electrons are waves