From Philosophical Idea to Scientific Theory The Atom: From Philosophical Idea to Scientific Theory

Particle Theory of Matter Dates back to 400 B.C. and Greek philosophers like Democritus Coined the term “atom” which meant “indivisible”

Experiments Advance In the 18th century several basic scientific laws develop.

Law of Conservation of Mass Mass is neither created nor destroyed during normal chemical reactions.

Law of Definite Proportions A chemical compound contains the same elements in the same proportions regardless of sample size or source.

Law of Multiple Proportions If two or more different compounds are composed of the same two elements then ratios of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.

John Dalton In 1808 an English schoolteacher proposed an explanation for the 3 basic laws. This became known as the Atomic Theory

Dalton’s Atomic Theory All matter is composed of particles called atoms Atoms of a given element are identical in size, mass and other properties. Atoms of different elements differ in size, mass and other properties.

Dalton’s Atomic Theory Atoms cannot be subdivided, created or destroyed Atoms of different elements combine in simple, whole number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated or rearranged.

Modern Atomic Theory As technology improved and more information became available Dalton’s theory has become modified.

Modern Atomic Theory Two basic tenets remain: All matter is composed of atoms Atoms of one element differ in properties from atoms of another element.

Assignment Read pages 65-68 Answer the following: Name the various compounds that the carbon atom was a component of in Levi’s story. Why was it unlikely for the carbon atom to have been taken into the bird’s bloodstream? Section Review pg. 69 (1-3)