CHEM 1F92 Chapter Notes -Picometre, Cathode Ray, Alpha Particle
Document Summary
5th century bc, greek philosopher democritus said that matter is made up of small, particles called atomos (uncuttable) In 1808 english scientist and teacher, john dalton, formulated a precise definition of atoms. His work marked the beginning of the modern era of chemistry. The atomic theory is based on the following: 1. Elements are composed of extremely small particles called atoms: 2. All atoms of a given element are identical: 3. Compounds are composed of atoms of more than one element, with the correct ratio. Law of definite proportions: different samples of the same compound always contain its elements in the same proportion by mass. Law of multiple proportions: different compounds made up of the same elements differ in the number of atoms of each kind that combine?: 4. Atoms cannot be destroyed or created in chemical reactions, only separated, combine, or rearranged. Law of conservations of mass: mater can"t be created or destroyed.