The atom’s history and theories

1. The atom’s history and theories

2. What's the size of water? media.nasaexplores.com/.../images/faucet2.jpg

3. Early History There must be ultimate tiny particles of water that could not be further subdivided. Look at the sand at the beach! Leucippus Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. www.mlahanas.de/Greeks/images/Leucippus1.jpg

4. Early History I’ll name these indivisible particles atomos (which means indivisible). These atoms are distinct in shape and size! 460 – 370 BC Democritus Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. web.mit.edu/philos/www/mm/democritus.jpg

5. Early History There are only four elements! Water Earth Air Fire Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. www.brown.edu/.../Images/0506/GREEKS131.jpg

6. Law of Conservation of Mass When a chemical reaction is carried out in a closed system, the total mass of the system does not change! 1743 – 1794 Antoine Lavoisier Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. http://www.lepla.edu.pl/fr/modules/Activities/m40/images/lavois03.jpg

7. total mass total mass Law of Conservation of Mass: The total mass of the system does not change product reactant 1 + reactant 2 = calcium oxide + carbon dioxide calcium carbonate 100.09 g 56.08 g + 44.01 g Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

8. Law of Definite Composition A given compound always contains its constituent elements in certain fixed proportions by mass! Proust 1754 – 1826 Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. http://www.provincia.ps.it/ls.laurana/tempo/proust.jpg

9. 10.00 g lead 11.56 g lead sulfide Law of Definite Composition: No matter the mode of preparation, a particular compound is composed of the same elements in the same mass fractions 1.56 g sulfur Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. http://clendening.kumc.edu/dc/pc/berzelius.jpg http://elements.vanderkrogt.net/images/Lead.jpg http://www.theodoregray.com/PeriodicTable/Samples/082.6/s7s.JPG

10. 10.00 g lead 11.56 g lead sulfide Law of Definite Composition: No matter the mode of preparation, a particular compound is composed of the same elements in the same mass fractions 3.00 g sulfur 1.44 g sulfur left-over Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. http://clendening.kumc.edu/dc/pc/berzelius.jpg http://elements.vanderkrogt.net/images/Lead.jpg http://www.theodoregray.com/PeriodicTable/Samples/082.6/s7s.JPG

11. 11.56 g lead sulfide Law of Definite Composition: No matter the mode of preparation, a particular compound is composed of the same elements in the same mass fractions 18.00 g lead 1.56 g sulfur 8.00 g lead left-over Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. http://clendening.kumc.edu/dc/pc/berzelius.jpg http://elements.vanderkrogt.net/images/Lead.jpg

12. Law of Definite Composition: No matter the source, a particular compound is composed of the same elements in the same mass fractions Analysis by Mass (grams/20.0 g) Mass Fraction (parts/1.00 part) 8.0 g calcium 2.4 g carbon 9.6 g oxygen 0.40 calcium 0.12 carbon 0.48 oxygen 20.0 g 1.00 part by mass Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

13. Law of Multiple Proportions Elements can combine in more than one set of proportions, and each set corresponds to a different compound! Dalton 1766 – 1884 Hill, J. and D. Kolb. 1995. Chemistry for Changing Times 7th ed. Phils: Prentice-Hall, Inc. http://cache.eb.com/eb/image?id=8421&rendTypeId=4

14. Law of Multiple Proportions: Elements can combine in more than one set of proportions Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

15. Atomic Theory • Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements. Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

16. Atomic Theory Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

17. Atomic Theory • Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction • Supports • Law of Definite Composition • Law of Multiple Proportions Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

18. Atomic Theory Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

19. Atomic Theory • A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction • Supports the Law of Conservation of Mass Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

20. Atomic Theory + Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

21. Based on Dalton’s Atomic Theory, the atom is • the basic unit of an element that can enter into a chemical reaction • extremely small • indivisible Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.