Chapter 2 - Atoms and Elements

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Published on 13 Apr 2011
Chapter 2 - Atoms and Elements
2.1 Imaging and Moving Individual Atoms
- Scanning Tunneling Microscopy (STM) found by Gerl Binning and Heinrich
Rohrer, is a technique that can image and move individual atoms/molecules
2.2 Early Ideas about the Building Blocks of Matter
- Leucippus (5th century B.C) and Democritus (460-370 B.C) theorized that matter was
composed of small, indivisible particles (atomos) Nothing exists except atoms and empty
2.3 Modern Atomic Theory and the Laws that Led to It
- 1789 (Antoine Lavoisier): The Law of Conservation of Mass In a chemical reaction,
matter is neither created nor destroyed
- 1797 (Joseph Proust): The Law of Definite Proportions All samples of a given
compound have the same proportions of their constituent elements
- 1804 (John Dalton): The Law of Multiple Proportions When 2 elements (A & B) form
2 different compounds, the masses of B that combine with 1g of A can be expressed as a
ratio of small whole numbers
- 1808 (John Dalton): Atomic Theory Each element is composed of tiny, indestructible
particles (atoms), All atoms in element have the same mass and properties that distinguish
themselves from others, Atoms combine in simple, whole number ratios to form compounds,
Atoms of 1 element cannot change into atoms of another element, only in a chemical
reaction can they change through being bound to one another
2.4 Discovery of the Electron
- In the late 1800s, J.J. Thomson (1856-1940) tried to uncover the properties of cathode
rays found that particles in rays were independent of composition and negatively charged
- In1909, Robert Millikan performed oil drop experiment which deduced the charge of the
single electron (-1.60 x 10^-19 C)
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