1. Chapter 2: General Chemistry Atoms, Molecules, and Ions

2. 2.1 ATOMIC THEORY OF MATTER -Dalton: all matter is composed of small particles called atoms.

3. POSTULATES OF DALTON’S ATOMIC THEORY 1.All matter is composed of atoms. Atom: extremely small particle of matter that retains its identity during chemical rxns. 2.Element: type of matter composed of only one kind of atom. Atoms of a given element have a characteristic mass. 3.Compound: type of matter composed of atoms of two or more elements chemically combined in fixed proportions. Ex. Water, 2 H, 1 O

4. 4. Chemical rxn.: rearrangement of the atoms present in the reacting substances to give new chemical combinations present in the substances formed by the rxn. Atoms are not created, destroyed, or broken into smaller particles by any chemical rxn.

5. ATOMIC SYMBOLS AND MODELS -Atomic symbol: one or two letter notation used to represent an atom corresponding to a particular element. Chlorine: Cl Sodium: Na (latin word natrium)

6. DEDUCTIONS FROM DALTON’S ATOMIC THEORY - Law of multiple proportions: when two elements form more than one compound, the masses of one element in these compounds for a fixed mass of the other element are in ratios of small whole numbers.

7. 2.2 THE STRUCTURE OF THE ATOM -Nucleus (positively charged, most mass) -Electron (negatively charged, light)

8. DISCOVERY OF THE ELECTRON - J.J. Thomson conducted a series of experiments that showed that atoms were not indivisible particles.

9. -glass tube with no air, cathode (-), anode (+). -When voltage is turned on the glass tube emits a greenish light. -Greenish light caused by the interaction of the glass with cathode rays (originates for the cathode). -Cathode rays move toward the anode, pass through hole to form beam

10. - Beams bends away from the negatively charged plate and toward the positively charged plate. Concluded that a cathode ray consists of a beam of negatively charged particles (electrons).

11. Youtube video of cathode ray http://www.youtube.com/watch?v=O9Goyscb azk http://www.youtube.com/watch?v=O9Goyscb azk

12. From this experiment Thomson could also calculate the ratio of the electron’s mass, m e. Millikan exp. – Observed how a charged drop of oil falls in the presence and in the absence of an electric field. – The charge on the electron is found to be 1.602 x 10^-19 coulombs (C) – Found mass of an electron to be 9.109 x 10^-31 kg.

13. THE NUCLEAR MODEL OF THE ATOM -Rutherford: idea of the nuclear model of the atom -Geiger and Marsden: observed the effect of bombarding thin gold foil with alpha radiation from radioactive substances such as uranium. -Found that most of the alpha particles passed through a metal foil as though nothing were there, but a few (1 in 8000) were scattered at large angles and sometimes almost backward.