Unit 5 - Mark Rosengarten

1) Prediction if Thompson was right. All alpha particles
pass right through the gold foil
2) Actual results: most alpha particles went right through,
a few were deflected and a few bounced back
The alpha particles, (a), are shot at the gold foil. Most of the alpha
particles go right though (b). A few were deflected (c). Rutherford
interpreted this as meaning that there must be a small, dense,
positively charged nucleus (d) in the center of the atom with empty
space making up the majority of the atom’s volume.
5) He saw the light! Broken up into bright lines though a spectroscope! Go, Neils Bohr! (1913)
His model of the atom
The atom is just like Rutherford says
it is, but the electrons travel in
energy levels around the nucleus.
When an atom is given energy, it
rises in energy levels. When the
electron falls back to its original
energy level, it gives off energy in the
form of light.
How he arrived at their model
Bohr observed the light given off when several elements are heated and give
off light. Different elements gave off different colors of light. When this light
was passed through a prism, the light was broken up into lines of color. Each
element’s lines were different. Bohr figured that electrons falling from high
energy levels to low energy levels were causing the light. Each element’s
spectrum of colored lines was different, meaning that the energy levels of
different elements have a different amount of energy. This process, called
spectroscopy, is useful for identifying element samples.
© 2011, Mark Rosengarten R 6