The Atom 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 18 th 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: l l 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: ¡ l l l 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)