By Nancy Mejia, Jose Guzman, Mike Popovac, Edgar Avalos

John Dalton 1766-1844

Was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory.

Was born into a Quaker family at Eaglesfield.

In 1800, Dalton became a secretary of the Manchester Literary and Philosophical Society.

In the following year he orally presented an important series of papers, entitled "Experimental Essays" on the constitution of mixed gases.

John Dalton studied the behavior of gases in air.

Dalton’s Theory states that all matter is made up of individual particles called atoms, which cannot be divided.

All elements are composed of atoms.

All atoms of the same elements have the same mass, and atoms of different elements have different masses.

Compounds contain atoms of more than one element.

In a particular compound, atoms of different elements always combine in the same way.

Five Main Points of Dalton’s Atomic Theory.

1. Elements are made of extremely small particles called atoms.

2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.

3. Atoms cannot be subdivided, created, or destroyed.

4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

5. In chemical reactions, atoms are combined, separated, or rearranged.

Dalton proceeded to print his first published table of relative atomic weights. Six elements appear in this table, namely hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus, with the atom of hydrogen conventionally assumed to weigh 1.

John Dalton’s use of the word “atom” was influenced by Democritus, Newton and the Hindu author Kanda.

John Dalton pictures atoms as tiny, indestructible particles, with no internal structure.

In summary, John Dalton developed a theory to explain why the elements in a compound always join in the same way. He proposed that all matter is made up of individual particles called atoms, which cannot be divided.