- Democritus proposed that all mater, the "stuff" that makes up the world around is, is actually composed of tiny, indivisible particles.
- He called them atomos, from which we get the English word atom.
- He would have said that you could not cut a piece of aluminum foil into infinitely smaller pieces. Eventually, you would divide the foil into individual atoms, which he thought could be divided no further.
- An atom is the smallest particle of an element that retains the chemical identity of that element.
Antoine Lavoisier:
- Lavoisier carefully measured the mass of substances before and after a chemical reaction and found that the masses were always equal.
- no mass was gained or lost in a reaction.
- A chemical reaction neither creates nor destroys matter, but the matter is conserved.
Joseph Louis Proust:
- Proust found that a given compound always contains the same elements in the same proportions by mass.
- For example, the mass of water is always 88.9% oxygen and 11.1% hydrogen.
John Dalton:
- Each element is composed of extremely small particles call atoms.
- All atoms of a given element are identical, but they differ from those of any other element
- Atoms are neither created nor destroyed in any chemical reaction
- A given compound always has the same relative numbers and kinds of atoms
By: Krysta Del Rosario
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