chapter 3-1: the atom- from philosophical idea to scientific theory

Democritus

Greek philosopher among the first to suggest the existence of atoms. Believed that atoms were indivisible and indestructible. Ideas did agree with later scientific theory, but did not explain chemical behavior, and was not based on the scientific method- but just philosophy

John Dalton

father of modern atomic theory

John Dalton's assumptions

Matter is composed of extremely small particles known as atoms. Atoms of a given element are identical in mass, size, and other properties; and are different from atoms of other elements.

John Dalton's assumption (continuation)

Atoms can not be sub-divided, created, or destroyed. Atoms of different elements combine in simple whole ratios to form compounds. In chemical reactions, atoms are combined, separate or rearranged.

Law of Conservation of Mass

Mass is neither created or destroyed during ordinary, physical, or chemical reactions.

Law of Definite Proportions

A chemical compound contains the same elements in exactly the same proportion by mass regardless of the size of the sample or sources of compound.

Law of Multiple Proportions

If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers. EX.) CO & CO2