3. Marie and Pierre Curie Worked with radioactivity and discovered three subatomic particles: ~ Alpha () ~ Beta () ~ Gamma (γ) These explain electrical charges in an atom.
4. J.J. Thomson ~ Studied charges in a Cathode Ray Tube. ~ Discovered through his experiment that atoms have negatively charged particles.
5. 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
6. 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.
7. Atomic Structure ~ Proton (p+) ~ Electron (e-) ~ Neutron (n) electron electron electron nucleus ~protons ~neutrons
8. Nucleus: ~ p+ and n ~ most of atomic mass ~ small ~ positive charge
9. Outside Nucleus: ~ contains e- ~ small light particles ~ occupy most of volume ~ negative charge
10. Atoms are neutral ~ Number of e- = number of p+ There are 3 electrons in this atom, how many protons are there?
11. On the Periodic Table of Elements: Atomic Number Symbol Name Atomic weight 1 H Hydrogen 1.0079
12. Mass Number ~ Not on Periodic Table. ~ Number of particles in the nucleus. ~ Equal to number of protons and neutrons.