The Chemicals in Your Life

I. Atoms

A. History
1. Static electricity has been around since ancient times, continuous electric current was discovered when Allessandro Volta invented the electrolytic cell. 1800. A chemical reaction releases electrons and these electrons flow through wire, and can do work. "GE brings good things..."
2. Voltage is a measure of how much current times the resistance that the current has to go through.
3. Faraday (1791-1867) and Davy (1778-1829) contributed to the discovery of electrolysis

a. electrolysis is the splitting of compounds by electricity
b. electrolytes conduct electricity when dissolved in water
c. electrodes are carbon rods or metal strips that carry electricity

(1) cathode is negatively charged
(2) anode is positively charged
d. cation is a positive ion, cations move toward the cathode
e. anion is a negative ion, anions move toward the anode
f. electrons flow from the cathode to the anode
g. Atoms have electrical properties

4. Crookes (1832-1919)--cathode ray tube, beam of light goes from the cathode to the anode
5. Tomsen (1846-1940) in 1897 showed that cathode rays were deflected by a magnetic field,

a. the rays were the same regardless of the type of gas in the tube or material in the electrodes.
b. cathode rays are beams of electrons, and all atoms have electrons

6. DEMO
7. Protons were discovered by Goldstein in 1886

B. Periodic table

1. Dalton--first observed trends
2. Mendelev--arranged elements by size and put elements with similar properties in columns, he even proposed the existence of undiscovered elements.

a. Tellurium is ahead of Iodine, so that Iodine could be lined up with the other halides
b. Tellurium is similar to sulfur and selenium

C. Parts is parts

1. Electrons, negative charge, 9.1 x 10-²⁸g
2. Nucleus

a. Protons 1837x bigger than electrons, positive charge, 1 amu
b. Neutrons, about the same size as a proton

II. Radioactivity

1. History
a. Roentgen--x-rays, can go through walls
b. Becquerel discovered radioactivity--photographic film was clouded by something coming from Uranium
c. Marie and Pierre Curie

(1) radiation is the spontaneous emission of radiation from unstable elements
(2) received physics Nobel prize together with Becquerel in 1903
(3) Marie got another chemistry Nobel prize 1911 for her work with Polonium and Radium
(4) She was the only double prize winner for 50 years

2. Alpha particle:

a. 2 protons, 2 neutrons
b. +2 charge
c. lowest energy, paper will protect
d. only dangerous if ingested

3. Beta particle:

a. mass of electron
b. negatively charged
c. higher energy
d. thick plastic will protect


4. Gamma particle

a. no mass, no charge
b. highest energy
c. must have lead shield to protect

III. Rutherford' s experiment

1. Hans Geiger--physicist
2. Ernest Marsden--undergraduate researcher
3. Alpha particles bombard gold foil, several were deflected

4. Its all relative

a. If an atom was the size of an indoor football stadium, the nucleus would be the size of a pea at the 50 yard line
b. The nucleus would weigh several million tons
c. A few flies flitting here and there would be the electrons

IV. Isotopes

1. Atomic number=number of protons, determines what element it is
2. Mass number=number of protons and neutrons combined

V. Models of the electronic structure

A. Bohr model

1. Ground states, excited states
2. spectroscopy--page 67

a. four lines for hydrogen
b. two lines for sodium

B. Quantum mechanical model

1. orbitals
2. filling orbitals
3. octet rule
4. electron configuration and the periodic table

VI. Periodic Table

A. Metals
B. Non metals
C. Metaloids
D. Family groups

1. alkali earth
2. alkaline earth
3. halogens
4. noble gases

E. Valence electrons

Please send comments to: koni@chem.csustan.edu

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Copyright © 1996 Koni Stone