atomic structure - foundations Flashcards
(perfect) black body definition
a hypothetical perfect absorber and radiator of energy with no reflecting power
black body radiation definition
any radiation that comes out of a black body
outline the ultraviolet catastrophe
applying classical physics to black bodies successfully predicts the intensities of the emissions of low frequencies but vastly overpredicted them at high frequencies
- solved by quanitisation
quantisation definition
the ideal that light exists as particle like packets of radiation = photons (meaning they have specific energies)
what is plancks constant?
the energy of a photon is proportional to its frequency, related by plancks constant
E = hv
outline the photoelectric effect
when radiation from light strikes a metal surface, electrons are ejected - if the frequency of the radiation is above a certain threshold (depends on metal) - provides evidence for the quanitisation of light
this ejection occurs at aa 1:1 ratio
define intensity of light
number of photons present
why does radiation only eject electrons if its above a certain threshhold
when electrons are hit by a photon there is a transfer of energy, but electrons need a minimum amount of energy to be ejected, photon energy becomes the kinetic energy of the elctron
wave-particle duality definition
there is evidence to prove than light/matter can behave both as a particle and as a wave, so it is treated as whichever is more convenient
how does atomic spectra provide evidence for quantisation?
atoms can absorb/emit electromagnetic radiation of certain frequencies, implying only certain frequencies are possible within an atom - this is observed on atomic spectra, which can therefore be used to study the internal electronic structure of an atom
how are atomic spectra made?
when certain frequencies of radiation/light are absorbed by an atom, causing electrons to be excited and move to a different subshell then seen as lines on the spectra - suggests electrons can only exist at certain energy levels within an atom (so electronic energy is quantised)
outline the function of the rydberg equation
used to determine how much energy is emitted when electrons change energy levels
what equation is used when considering wave particle duality?
λ = h/mv
where λ = wavelength m
h = plancks constant
m = mass kg
v = velocity
outline the heisenberg uncertainty principle
since electrons have wave properties, it is impossible to know their precise position + momentum simultaneously - this applies to other things with wave particle duality
ΔρΔq >= h/4π
where Δρ = uncertainty in momentum
Δq = uncertainty in position
h = plancks constant
give the momentum equation
ρ = mv = mass * velocity
how does uncertainty principle relate to size of electrons ?
because of the uncertainty principle, since electrons are so small, you cannot localise an electron to a very small space without giving it a very large momentum
why are electrons probabilities?
as the precise location of electrons in atoms cannot be known, we instead use probabilities of the electron being in certain volumes of space
what is schrodingers wave function
a function with that describes the wave of an electron in an atomic orbital
it has 2 parts:
the radial function - describes the wave in terms of distance rom nucleus (r)
angular function - describes how amplitude of wave varies with direction
what is a limitation of schrodingers wave function?
it only forms for 2 body problems - nucleus + 1 electron
what does it mean if the wavefunction = 0
this is a node
what is the Born interpretion?
the square of the wavefunction, which is proportional to the probability of finding an electron within a small volume of space
what are the implications of wave-particle duality on position of electrons in atoms?
as schrodingers equation treats electrons as waves, the electrons are spread out (delocalised) so wave mechanisms is in terms of probability, where probability per unit volume = electron density
what does solving schrodingers equation give you?
the specific energies that are possible for electrons within atoms
amplitude definition, in an atomic wave function
the value of electron wave at any point in space
