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Tuesday!!!!! 11/1/11 PowerPoint Presentation
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Tuesday!!!!! 11/1/11

Tuesday!!!!! 11/1/11

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Tuesday!!!!! 11/1/11

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  1. Tuesday!!!!!11/1/11 Bell Ringer Schedule PAP Chemistry • Bell Ringer • CH. 5 Notes • Flame Test Pre-lab HOMEWORK: Print Ch. 5 Notes I CAN……solve chemistry problems by being an independent, creative thinker. Teachers open the door, but you must enter by yourself.  • Get out your Ch. 5 book pages and your notes we started.

  2. Dalton • Proposed model for atom • Dalton’s Atomic Theory • Elements composed of atoms • Atoms of same elements are alike in mass and size*** • Atoms of different elements have different mass and size • Chemical compounds are formed by the union of two or more atoms of the different elements • Atoms combine to form compounds in simple numeric ratios • Atoms of two elements may combine in different ratios to form more than one compound • Modifications to Dalton’s original theory: • Atoms are composed of subatomic particles • ***Not all atoms of same element have the same mass • Under certain circumstances, atoms can decompose

  3. Use of Models • Models are used to explain behavior • Dalton’s Atomic Model: • Explains behavior of atoms, compounds and molecules • Modifications made when new information arises

  4. Law of Definite Composition • Compounds contain two or more elements chemically combined in definite proportions by mass • Water is always a 1 : 2 ratio, oxygen to hydrogen • Hydrogen peroxide is always a 2 : 2 ratio, oxygen to hydrogen

  5. Law of Multiple Proportions • Atoms of two or more elements may combine in different ratios to produce more than one compound • CuCl CuCl2 • CH4 C8H18

  6. Significance of the two Laws…why are they so important??? • Composition of a substance will ALWAYS be the same • Composition of different compounds formed from the same elements will be unique

  7. Law v. Model • Law • Summary of observed behavior • Remain constant • Model (theory) • Attempt to explain the observed behavior • Can be modified

  8. Electric Charge • Positive • Negative • Unlike charges attract • Like charges repel • Charge may transfer form one object to another: induction or contact • Induction: influence of a charged object, NOT BY CONTACT

  9. Force, charge and distance F = kq1q2 r2

  10. Ions ( Faraday and Arrhenius) • Positive = cations • Negative = anions • Gain or transfer of electrons (Stoney / Thomson)

  11. Subatomic Particles • Electron (Thomson) e- • Negative charge • Mass 9.11 x 10-28 g • Proton (Goldstein, Thomson) p+ • 1.637 x10 -24 g • Positive charge • Neutron (Chadwick) n° • Neutral charge • 1.675 x10 -24 g

  12. Rutherford and the Nucleus of the Atom • Gold Foil Experiment Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.Bottom: Observed results: a small portion of the particles were deflected, indicating a small, concentrated positive charge. Note that the image is not to scale; in reality the nucleus is vastly smaller than the electron shell.

  13. Atomic Arrangement • What makes an atom neutral? • Same number of protons and electrons

  14. What do the numbers mean? • Atomic # = # p+ • Whole number increasing from left to right on the periodic table • # p+ = # e- • Mass number = n° + p+

  15. Isotopes • Atom with same atomic number and different numbers of neutrons in nucleus of atom

  16. Isotopes • Most elements occur in nature as mixtures of isotopes • Not all are stable • Radioactive isotopes • Decompose

  17. Atomic Mass • Atomic mass or atomic weight • Measured in atomic mass units or amu • Atomic mass is average relative mass of all naturally occurring isotopes of that element • The atomic mass of an element is compared to the atomic mass of carbon-12 (12.00 amu)