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450 BCE
The term atoms is created.
emocritus wondered what would happen if you cut a piece of matter, such as an apple, into smaller and smaller pieces. He called these "uncuttable" pieces atomos. This is where the modern term atom comes from. -
dalton created a theory
- all substances are made of atoms - atoms of the same element have the same amount of mass - atoms form compounds; a compound always has the same kinds of atoms in the same ratio People still accept this theory but the part that is no longer believed in is that atoms are the smallest particles
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subatomic particles were discovered
J. J. Thomson proposed the plum pudding model of the atom. In this model, negative electrons are scattered throughout a "sea" of positive charge -
Ernest Rutherford discovered the nucleous.
1911: Ernest Rutherford discovered the nucleous. some elements give positively charged particles. He made a model in which he threw tennis balls at gold foil. Most of the balls go throw the foil. 1 in 1800 balls bounce back because sometimes they repel from the positive charged particles -
Niehls Bohr expanded Rutherford's nuclear model
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scanning tunneling microscopes were invented to see atoms