Absorption And Spectroscopy Flashcards
What is the relationship between wavelength and frequency
As wavelength increases, frequency decreases
Frequency is directly proportional to energy
What is wavelength
Wavelength is the distrance from peak to peak of a wave
How do you calculate change in energy
What happens when electrons absorb light
They can move electrons from a low energy orbital to high energy orbital
(Low energy level to high energy level)
What would happen if electrons are moved to a higher energy level due to absorbing energy
This would break the bond (which proves that bonds have energy)
You have to put energy in to break bonds
How much energy would be required to excite an electron
The amount of energy associated with that would be the frequency of light used to break the bond
If the gap between the orbitals is large then this would require a lot of energy and would therefore be unobservable as its outside the visible region
The greater the amount of energy absorbed= the higher the energy level of the orbital to which the electron moves
How is absorbance measured
How does a spectrophotometer work
Spectrophotometer puts light in
Photomultiplier reads amount of light that comes out (how much the transmitted intensity is reduced from the input intensity - transmittance)
All absorbances will be greater than 0
What is I0 and I
How can absorbance be calculated
If transmittance was 100% what would absorbance be?
0
Why are there broad peaks on an absorbance spectrum
This is because there is additional ways that the energies are stored in a molecule
There is molecular motion (molecules move in different ways)
Which electronic transition is most likely to occur in an atom or molecule
The transition that has the lowest energy
What is needed for electronic transitions to occur
Without anti bonding orbitals, electronic transitions can’t occur
What does conjugation do
Gives us the ability to absorb light at a longer wavelength and lower energy so moves things into the visible region -> so can be observed
What is beer-lamberts law
Related absorbance to concentration and length of path through which light is passing
How can absorbance be calculated using beer-lamberts law
What do the horizontal lines on this image represent
They represent the relative energies of different orbitals
As you go up, energy of the orbital increases
Where will electrons accumulate when they absorb energy
They will accumulate at the lowest energy excited state
What happens when electrons fall back to ground state
Will emit a small amount of energy
What is spectroscopy
What do the peaks on an absorption spectrum represent
What is a valence shell
Outermost shell occupied by valence electrons
What is electron excitation
What is the effect of an atomic species having higher energy
What is a transmission spectrum
Measures how much radiation is being transmitted through the sample
