2 Michael FaradaySuggested that the structure of atoms is related to electricity, and it turns out that atoms contain particles that have electrical charge.
3 Static ElectricityBenjamin Franklin is one of the first to experiment with electricity.Concludes that electricity has two kinds of charges.Positive (+)Negative(-)
4 Cathode Rays and Electrons Running electricity through a partially evacuated glass tube occurs in a cathode tube.
5 The negative end is called a cathode. The positive charged end is called an anodeWhen lined with a fluorescent material and passing electricity through it, you can see the radiation going through it.
6 It was found that putting a magnet near the particles deflects them, indicating a negative charge of particlesJ.J. Thomson experimented with cathode rays, with a magnet, and charged plates near the ray.
8 Discovered Magnetic and electric fields deflect the rays Deflects rays in predictable waysThe particles are Negative in chargeParticles come from cathodeNamed the particles ElectronsMeant Atoms were made smaller parts!!!!Particles had a charge of 1.76 x 108 coulombs/gram
9 Robert Millikan Oil Drop Experiment Gave droplets of oil a negative charge using x-raysDroplets fell between two charges plates.Measured how the charge on the plates affected the rate of fall of oil drops.Found the charge to be 1.60 x coulombsFrom Thomson's findings he could calculate the mass of a single electron.9.11 x grams
13 RadioactivityRadioactive elements are found in the late 1800’s. Henri Becquerel was the first to discover radioactivityMarie Curie and her husband Pierre find two radioactive elements after Becquerel
14 Ernest Rutherford See Figure 3-13 in book Discovers alpha particles Deflects towards negative plateDiscovers beta particlesDeflect towards positive plateDiscovers gamma particlesNot affected by electric plates
15 The Nuclear AtomJ.J. Thomson's problem again: if electrons are negative, why are atoms neutral?Must contain positive parts equal to the negative parts.Where are they?The Plum Pudding ModelAll particles evenly distributed.Rutherford changes this concept
17 Most particles passed through gold without a problem1 in 8000 alpha particles deflectedThese were sent in ALL directions including straight back!
18 What does this mean?Most of the atoms positive charge, as well as the mass is in the middle, called the nucleus.Most pass through the empty space but occasionally one gets close enough to the positive nucleus to deflect