2.1 - Dalton's Atomic Theory

Law of Conservation of Mass

A law stating that the mass of the substances produced in a chemical reaction equals the mass of the substances that reacted.

Law of Definite Proportions

A law stating that all samples of the same pure compound will always contain the same proportions by mass of the component elements.

Dalton’s Atomic Theory

1. All matter is composed of exceedingly small, indivisible particles, called atoms.

2. All atoms of a given element are identical both in mass and in chemical properties. However, atoms of different elements have different masses and different chemical properties.

3. Atoms are not created or destroyed in chemical reactions.

4. Atoms combine in simple, fixed, whole-number ratios to form compounds.

Subatomic Particles

The smaller particles which make up atoms.

Scanning Tunneling Microscopy (STM)

Because atoms are too small to be seen with an optical microscope, images could not be produced until the invention of the STM in the 1980s.