History of the Atom

Chemistry Creds (History):

Democritus (460 BC – 360 BC)

Ancient Greek philosopher

▪No experiments performed!

Major Contribution: The Atom

He proposed that everything was made of these "atoms,"

and that they are indivisible (you can't break them down).

John Dalton (1766-1844)

Major Contribution: Atomic Theory (1808)

▪This began the modern era of chemistry

Four Principles:

1) Elements are composed of indivisible particles called atoms.

2) All atoms of a given element are identical.

3) Compounds are composed of atoms of one or more elements,

and will form only in whole-number ratios.

This is called the Law of Multiple Proportions

H2O exists, while H2.35O does not.

4) A chemical reaction involves the combination, separation, or rearrangement of atoms, NEVER their creation or destruction.

This is called the Law of Conservation of Mass

John Dalton implied what Newton later stated:

"Matter can neither be created Nor destroyed!"

J.J. Thomson (1856-1940)

Major Contribution: The Electron

Also came up with the "Plum Pudding Model" of the atom, which said that an atom is a pudding of these charged parts.

Ernest Rutherford (1871-1937)

Below are two videos on the history of the atom. The first video with Tyler DeWitt is for a general understanding and covers most of what you need to know.

*If you have definitely got this material down, challenge yourself and check out the crash course version with Hank Green (2nd vid) below!

Video #1: Basic History of Atomic Discovery with Tyler DeWitt: