John Dalton (1766 - 1844)

Dalton's Elements and Compounds (1808, 1810,1827)

number 21 is water, HO

Dalton's atomic theory:

• matter consists of atoms

• atoms can not be created or destroyed

• all atoms of the same element are identical

• different elements have different types of atoms

• chemical reactions involve rearrangements of atoms

• compounds consist of "compound atoms" (molecules) composed of atoms from the constituent elements

Problems:

• assumed all gases were monoatomic, e.g. oxygen is O

• assumed simplest compounds were binary, e.g. water is HO

• his atomic weights were approximate

• no knowledge of isotopes

davy