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Development of the ATOMIC THEORY

Development of the ATOMIC THEORY. Early Studies of Matter. The Greeks – more than 2000 years ago Four Elemental Substances: Fire, Earth, Wind, and Water. Matter made up of particles. Democritus – 460 BC. Proposed that all matter is made up of indivisible particles that he called

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Development of the ATOMIC THEORY

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  1. Development of theATOMIC THEORY

  2. Early Studies of Matter • The Greeks – more than 2000 years ago • Four Elemental Substances: • Fire, Earth, Wind, and Water Matter made up of particles...

  3. Democritus – 460 BC • Proposed that all matter is made up of indivisible particles that he called • Aristotle disagreed…so Democritus’ theory remain dormant until Dalton. ATOMS

  4. Democritus vs. Aristotle source source

  5. Robert Boyle - 1661 • Proposed that matter is composed of simple substances called elements that cannot be further decomposed or broken down. Qualitative Data

  6. Antoine Lavoiser - 1772 • Importance of • First stated Measurements Law of Conservation of Matter "Father of Modern Chemistry"

  7. Conservation of Mass H2 (g) + O2 (g)  H2O (l) 20 g + 160 g  180 g Mass is neither created nor destroyed!

  8. J. Proust – 1799 • In a pure compound, the elements combine in definite proportions to each other. Law of Definite Proportions

  9. Law of Definite Proportions decomposes H2O (l)  H2 (g) + O2 (g) 450 g  50 g + 400 g 90 g  10 g + 80 g When water decomposes the ratio of the mass of O2 to H2 is always 8:1

  10. Law of Multiple Proportions • Two elements can combine to form more than one compound ` • Ratio of the masses always a wholenumber! C + O  CO 1.00 g + 1.33 g  2.33 g C + O +O  CO2 1.00 g + 2.66 g  3.66 g 2:1

  11. John Dalton & Atomic Theory 1803 source Quantitative Data source

  12. Dalton’s Atomic Theory • Matter is composed of very small particles called atoms. • Atoms are indivisible and cannot be created or destroyed.* • All atoms of a given element are identical.* • Atoms of different elements are different. • Different atoms combine in whole numberratios to form compounds. • In chemical reactions, atoms are combined, separated or rearranged.

  13. Dalton’s Model of the Atom • Solid, indivisible sphere • Analogy: BILLARD BALL

  14. So Dalton’s atoms are kind of like billiard balls. Atoms combine in whole-number ratios.

  15. In a reaction, atoms are rearranged. + +  +

  16. So how big is an atom? • Most atoms are 1-2 angstroms across. • An angstrom = 1 X 10-10 m. • 6 Billion Copper atoms in a line -less than 1 meter!

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