Dalton’s Atomic Theory
1. Each element is formed of extremely small particles called atoms.
2. Atoms of a given element are identical; atoms of different elements differ in
some fundamental ways.
3. Chemical compounds form when atoms combine with one another. A given
compound always has the same relative number and types of atoms.
4. Chemical reactions involve reorganization of the atoms. Atoms change the
way they are bound together. During the process, atoms are NOT created or
Atom: the smallest particle of an element that can exist. They differ as a function of
their mass and other properties.
Element: a substance composed of only one kind of atom.
Elements can exist as single atoms or molecules.
Molecules are a definite and distinct group of atoms bound together.
Allotropes: different forms of the same element that exist in the same physical state
at the same temperature and pressure. (Ex. O2, O3. Oxygen and Ozone.)
Compound: a substance that consists of two or more different elements with their
atoms in a definite, characteristic ratio. (Ex. H2O, CO2, CO. Water, Carbon Dioxide,
Language of Chemistry: Intro to Nomenclature
Types of Elements:
1. Non-metals: do not conduct electricity, are not malleable or ductile.
2. Semi-Metals: show mixtures of metallic and non metallic properties.
3. Metals: conduct electricity, have metallic luster and are malleable and ductile.