Quantum Model of the Atom Flashcards
What is the dotpoint of this topic?
De Broglie’s contribution
Experimental evidence
Link to Schrodinger model
What is the idea that de Broglie propose?
electrons have dual particle/wave nature
What is the formula that Broglie proposed?
λ = h/p = h/mv
What experiment confirmed de Brog idea?
Davisson-Germer Experiment
Outline the Davisson-Germer experiment.
Investigation of scattering of low energy electrons from a nickel target in a vacuum.
Describe how the DG experiment worked.
Electrons from a heated filament are acclereated. The resultant beam, made up from electrons travel to the nickel crystal. The beam ‘reflected’ from the crystal surface enters the detector.
What did the DG exp conclude?
Showed that the scattered electrons exhibited intensity of maxima and minima at specific angles. The electrons were scatted by diff layers within the lattice and were undergoing interference. When they calcualted diff pattern, it was consistnet with de brog hypothesis
Why did De Brog improve the gaps of Bohr’s?
Bohr could not justify why the stable orbits were stable (and not cont. radiating and piralling)
- no justificaton for the quantisation of angular momentum
- wave theories
- intereference (standing waves) solved the probelms
What was Schrodinger’s model of the electron?
Used to describe wave mechanics - discrete and correspond to standing waves
- electrons could move in three dimensions
assumes that the electron is a wave and tries to describe the regions in space, or orbitals, where electrons are most likely to be found.
Explain how de Broglie believed electrons worked.
De Broglie used wave theories of matter to resolve problems with the stability of electron orbits in the Bohr atom. Additionally, De Broglie also used interference to resolve the problem, postulating that stable orbits are standing waves.
What is the fundamental principle of de broglie?
An electron can orbit an atomic nucleus only if the circumference of the orbit is a whole number of electron
wavelengths, so that it forms a standing wave. This way the electron is not accelerating.
- An orbit of radius r will be required to satisfy the condition: nλ = 2πr
What occurs when the electron travels around the orbit?
If the electron wave travels around the circular orbit, it will return to the same place and superimpose with itself,
leading to interference.
explain how the interference pattern works with the electrons
If it ravels a whole number of wavelengths around the circumference, it will be in phase with itself at every
position, hence it will constructively interfere. This is what forms the standing wave.
- If it does not travel a whole number of wavelengths around the circumference it will eventually be out of
phase with itself. This would lead to destructive interference and will not form a standing wave.
