atomic physics Flashcards
Geiger-Marsden experiment
most of the charged particles passed through gold foil, minor scatterings
Rutherford’s conclusions from gold foil experiment
positive charge concentrated in nucleus, and most of the mass located there. atoms are almost all empty space
radii of nuclei from charged particle scattering
loss of kinetic energy=gain of electrostatic potential energy
nuclear planetary model
Rutherford from gold-foil experiment
electrons orbit nucleus with electrostatic attraction providing needed centripetal force
limitations of nuclear model
electrons should be accelerating, radiating electromagnetic radiation and gradually losing energy, but this does not happen
atomic spectra
all objects emit electromagnetic waves, but at different wavelengths (solids mostly continuous, individual atoms don’t and are characteristic of the atom)
absorption by gas at same frequencies it would emit (example of resonance)
experiment to find atomic emission spectra
high voltage through two electrodes at ends of sealed glass at low pressure (electrons are emitted by cathode towards anode by electric field)
diffraction grating used to disperse light into spectra
production of absorption spectra
a white light sent through a glass container with a low pressure gas, is then dispersed with a grating
fraunhofer lines
dark lines showing the elements in an atmosphere due to absorption
evidence for atomic energy levels
emission and absorption spectra of gases at low-pressure consist of discrete lines
evidence for quantization of energy in atoms
atomic spectra, when a photon is emitted, then its energy must be equal to the difference of the energy between the different electron energy states in between emissions. therefore can only take certain energy levels
when is a photon emitted or absorbed
emission when electrons lower energy level, or absorb when increase
conversion of electron volts to J
eV=1.60217657 × 10-19 joules
de Broglie hypothesis
since photons have momentum p=h/wavelength, he suggests all particles have wave-like properties and wavelength (wavelength=h/p=h/mv)
wave-particle duality
all matter and energy exhibits wave-like and particle-like properties
