Atomic Theory

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Dalton's Atomic Theory

English chemist John Dalton (1766-1844) completed the first attempt at describing all matter in terms of atoms and properties.

Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.

Dalton based his theory on the law of conservation of mass and the law of constant composition.

The first part of his theory states that all matter is made of atoms, which are indivisible.

The second part of the theory says all atoms of a given element are identical in mass and properties.

The third part says compounds are combinations of two or more different types of atoms.

The fourth part of the theory states that a chemical reaction is a rearrangement of atoms.

Parts of the theory had to be modified based on the discovery of subatomic particles and isotopes.

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Molecules and Compounds

There are two major types of chemical bonds:

Covalent bonds are formed when two atoms share electrons.

Ionic bonds are formed by ions opposite in charge after electrons are swapped.

Compounds formed through covalent bonding are called molecules.

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Formulae and Models