University:
Shippensburg University of Pennsylvania
Course:
CHM 121 | Chemical Bonding
Academic year:

2023
Views:

245

Pages:

3
Author:

Carissa Thomas

The Atomic Theory • In the fifth century B.C. Democritus & Greek philosophers proposed: all matter is made up of very small indivisible particles. • Named them as «Atomos», meaning uncuttable or indivisible. • This idea was not quite accepted by others; Plato and Aristotle! • Aristotelean philosopy dominated for many centuries; -> 4 elements + the aether • Still, the notion of atoms endured and reemerged in seventeenth century. • Experiments in the eighteenth and nineteenth centuries led to an organized atomic theory by John Dalton in the early 1800s: – The law of constant composition – The law of conservation of mass – The law of multiple proportions • The Law of Constant Composition (Law of Definite Proportions) – Joseph Proust – 1799: -> Compounds have a definite composition. That means that the relative number of atoms of each element in the compound is the same in any sample. All samples of a compound have the same composition – the same proportion by mass of the constituent elements. -> The numbers of atoms of the elements in a given compound must always exist in the same ratio. Water H2O -> This law was one of the laws on which Dalton’s atomic theory was based. Carbon dioxide CO2