Published on February 27, 2011
By: Katelin Troy
Some History: Henry Baquel Found that Uranium ore emitted rays.
Marie and Pierre Curie Worked with radioactivity and discovered three subatomic particles: ~ Alpha () ~ Beta () ~ Gamma (γ) These explain electrical charges in an atom.
J.J. Thomson ~ Studied charges in a Cathode Ray Tube. ~ Discovered through his experiment that atoms have negatively charged particles.
Robert Millikan ~ Worked with charged oil drops in a chamber. ~Discovered the charge and mass of electrons and protons: Electron - Charge= -1 - Mass= 9.1094 * 10-28 g Proton - Charge = +1 - Mass = 1.6726 * 10^-24g
Earnest Rutherford Worked with gold foil experiment - Charged particles were aimed at Au atoms. Conclusions: - An atom has a small positive middle, aka the nucleus. - Most of the volume of the nucleus is taken up by electrons.
Atomic Structure ~ Proton (p+) ~ Electron (e-) ~ Neutron (n) electron electron electron nucleus ~protons ~neutrons
Nucleus: ~ p+ and n ~ most of atomic mass ~ small ~ positive charge
Outside Nucleus: ~ contains e- ~ small light particles ~ occupy most of volume ~ negative charge
Atoms are neutral ~ Number of e- = number of p+ There are 3 electrons in this atom, how many protons are there?
On the Periodic Table of Elements: Atomic Number Symbol Name Atomic weight 1 H Hydrogen 1.0079
Mass Number ~ Not on Periodic Table. ~ Number of particles in the nucleus. ~ Equal to number of protons and neutrons.
Nuclear Symbols: Mass # A X Atomic # Symbol Z Examples: Na Br 22 80 11 35
Isotopes: Atoms of the same element with different mass numbers. Example: Hydrogen Isotopes Hydrogen Deuterium Tritium 3 H H H 1 2 1 1 1
The End The End
Works Cited: Moore, John, et al. Chemistry The Molecular Science. Belmont, CA: Brooks/Cole, 2011. Print.
Photos and Diagrams Cited: Slide 2: http://www.flickr.com/photos/52307935@N00/291472553/sizes/l/in/set-72157594358781695/ Slide 7, 11, 13: Katelin Troy Slide 15: http://www.flickr.com/photos/d-kav/4428566547/sizes/o/in/photostream/
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