spectroscopy and analysis Flashcards
what is the frequency of an electromagnetic radiation?
cycles per second
relationship between wavelength and frequency?
wavelength inversely proportional to frequency
what is the speed of light in a vacuum?
3 × 10^8 ms^-1
how to calculate speed of light?
c= wavelength * frequency
what does a higher frequency on a visible colour spectrum mean?
the higher the frequency the shorter the wavelength
therefore the higher the energy
what is the order of electromagnetic spectrum form higher to lower energy (shorter to longer wavelength)?
gamma, X-ray, UV, infra-red, microwave, radio
what is the energy of photons given by?
E=hv
h is Planck’s constant
what is the value of Planck’s constant?
6.626 × 10^-34 m^2 kg s−1
what happens during spectroscopy?
EMR with specific frequency is absorbed by molecule which then becomes excited
does electromagnetic radiation have a range of frequencies corresponding to what?
electronic transitions
what happens to the electron after radiation is absorbed?
electron promoted to a higher level
what is an orbital?
region of space that can hold a maximum of two electrons with opposite spins
when will hydrogen atoms absorb photons?
hydrogen atoms will absorb photons with frequencies that agree with the differences between energy levels
what is λmax?
wavelength of a sample that has the highest absorbance
why are absorption broader as molecules become more complex?
more vibrations and rational energy levels
what happens as conjugation increases?
gaps between HOMO and LUMO decreases
difference between atomic and molecular absorption?
atoms have a sharp spectra
molecules have broad spectra
what is transmission?
fraction of light intensity that has passed through a sample unchanged
what is the equation of absorbance (A)?
A=-log T
what is the equation of transmittance?
T= I/I0
what is lamberts law?
A proportional the l
l (path length)
what is the beer lamber law?
A is proportional to c
c (concentration)
what is the beer lambert equation?
A= εcl
what is molar extinction?
the absorbance of 1 mol dm-3 sample with path length of 1cm
what layout does the beer lambert equation have?
A= εl * c
y= m * x
how can a bond be approximated?
spring between two spheres
equation for wavenumber (ṽ)?
ṽ =1/λ
what does a high wavenumber mean?
high frequency
what does increasing bond strength between two spheres do?
increasing bond strength increases frequency
what does decreasing size of spheres do?
increases frequency
what are the two components of electromagnetic radiation?
magnetic field going in the x-axis
electric field going in the y-axis
what is a photon?
little packet of energy that goes in the same direction as light
what is spectroscopy defintion?
‘study of the interaction between
electromagnetic radiation and matter’
what is monochromator?
one colour with a specific wavelength that is split
where are the electrons in an orbital
orbital is where 95% of the electrons will be found
why are electrons further away from the nucleus harder to remove?
electrons further away form the nucleus are harder to remove because they’re at a higher energy level
‘the difference between energy in vibrational energy levels matches the infra-red part of the electromagnetic spectrum’
what happens to a bond when it absorbs photons?
when bonds absorb photons its amplitude increases
frequency remains the same
what does doubling concentration do to absorbance?
doubling concentration doubles absorbance
what is spectroscopy?
‘The study of the interaction between electromagnetic radiation and matter.’
THz to Hz?
1THz =1 *10^12 Hz
GHz to Hz?
1GHz= 1 *10^9
MHz to Hz?
1MHz= 1*10^6
nm to m?
1nm = 1*10^-9 m
pm to m?
1pm = 1*10^-12
micrometer to cm?
1micrometer = 1*10^-4cm
units of each component in beer-lambert law?
molar extinction = dm3 mol-1 cm-1
conc = mol dm-3
path length = cm
what does decrease in electronegativity do to the vibrational frequency?
decrease
