Quantum Theory Flashcards
Quantized
Limited to only specific, distinct (discrete) energies
Non-continuous
Quantum
Small, discrete, indivisible quantity
Photon
Quantum of light
Black Body Radiation
- as object heats up, initially glows “red hot” then, higher temp., “white hot”
- temp rises more light, approach ideal “black body radiation”
- black body: idealised body that absorbs all EM waves
- it heats up, so its electrons produce EM waves
- hotter = higher frequency
- explains why hotter objects (i.e. sun) emit visible light
- peak wavelength (most intense)
- graph of light intensity (brightness) vs wavelength (colour): bell curve
Max Planck
- energy released by hot objects is proportional to the frequency of viration of their atoms
- explaining bell curve: energy is quantized (non-continous)
Energy of a quantum formula
E=hf=hc/λ
h=6.63*10^-34 Js (Planck’s constant)
Fundamental relation (speed, wavelength, frequency)
c=λf
Double Slit Experiment
1801, Thomas Young
- monochromatic light is passed through two thin slits and detected on a detection screen
Conclusion: light behaves as a wave
- two crests/troughs meet = constructive interference
- crest and trough = destructive interference
INTERFERENCE PATTERN OBSERVED
Photoelectric Effect
Heinrich Hertz and Philip Lenard observed that electrons are emitted from certain metals as a result of absorbing energy from EM radiation (light)
- emitted electrons = photoelectrons
- red light = no electrons (intesity has no effect)
- UV = electrons (intensity increase: more photoelectrons)
Albert Einstein
- explained through light having particle properties
- higher frequency = higher energy
- minimum amount of energy required to eject electron
- increasing intensity increases # of photons
Photoelectric Effect Formula
E(k max) = (mv^2)1/2 = hv - ϕ
Wave-Particle Duality
Light acts as both a wave and a particle
Louis de Broglie
- proposed that particles also have wave properties
- E=hc/λ and E=mc^2 } λ=h/mc
- electron behaves like a standing wave bound to nucleus
- explains quantized energy: wavelength must fit circumference of orbit exactly (define number of allowable wavelengths)
Werner Heisenberg
- due to dual nature of matter, impossible to know position and momentum of a particle exactly at the same time
- HEISENBERG UNCERTAINTY PRINCIPLE
- the act of determing where an electron is disturbs it
- uncertainty is about the size of the electron
Δ(mvx) * Δx ≥ h
Δ(mvx) - uncertainty in momentum
Δx - uncertainty in position
h - Plank’s constant
Erwin Schrodinger
- conventional wave equations to develop a probabilistic quantum model of atom
- solution: wave funtion 𝚿 defines probability of finding electron at any given location (MATH DESCRIPTION OF ELECTRON)
- region of probability = orbital
- equations gave 3 quantum numbers
H𝚿 = E𝚿
H - Hamiltonian (set of math instructions to be performed on 𝚿)
E - allowed energies for the electron/atom
Max Born
- used Schrodinger’s equations to develop probability functions that produce a plot of probability densities
- define a 3D volume around the nucleus with 90% probability of finding electron = orbital
- 𝚿^2 is the probability of an electron being at a given location
