CHE 150 Lecture 2: CHE 150- Lecture 2- Atoms and Molecules
Document Summary
The british chemist john dalton is credited with the formulation of the atomic theory of matter. Atomic theory offers an explanation of the structure of matter in terms of combinations of very small particles. There are four postulates that define dalton"s theory. Postulate #1: all matter is composed of indivisible atoms. An atom is an extremely small particle of matter that retains its identity during chemical reactions. Postulate #2: an element is a type of matter composed of only one kind of atom, each atom of a given element having the same properties. Thus the atoms of a given element have a characteristic mass. Postulate #3: a compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions. The relative numbers of any two kinds of atoms in a compound occur in simple ratios. Water, for example, consists of hydrogen and oxygen in a 2 to 1 ratio.
