Spectroscopy

what happens to a compound when a photon of colored light is absorbed?

the complimetary color of the absorbed wavelengths is perceived

what equation is used to describe the energy of the photon?

E=hν

before the absorption of a photon by the compound where are the electrons located?

lowest energy orbital possible; the ground state

when a photon of visible radiation is absorbed by a compound, where are its electrons located?

from an occupied, lower energy orbital to an unoccupied, higher energy orbital, or the excited state

what is transmittance?

the amount of light that passes through a solution

what type of instrument is used to measure the light absorbed by a solution?

spectrophotometer/spectrometer

what is the name of the solution containing vessel used in this instrument?

cuvette

what is an absorption spectrum?

a plot of the absorbance of a sample as a function of wavelength

what is Beer Lambert’s law?

for dilute solutions, the amount of light absorbed at a specific wavelength is directly proportional to the concentration of the solution

what is an absorption spectrum used for?

to determine the best wavelength of absorbance; highest = best

what is a Beer Lambert’s law plot and how is it created?

a calibration curve of absorption plotted as a function of concentration; absorbances of at least 3 solutions of known concentrations are measured

what element is an exception to electron configuration?

copper

what is the emission of electrons when EMR strikes the surface of a material?

photoelectronic effect

what is one application of the photoelectronic effect?

solar cells

the Greek symbol lambda represents?

wavelength

the Greek symbol nu represents?

frequency

the number of wave peaks passing a specific area per second is known as?

frequency

what is the speed of all forms of EMR?

3.00 × 10^8 ms^-1

what is visible light spectroscopy?

the study of the interaction of radiation from the visible part of the EM spectrum with a chemical species

what instrument measures how much color is absorbed by an object or substance?

colorimeter

what are the three variables associated with absorbance?

molar absorptivity coefficient, concentration, path length of light

what are transitions in molecular rotational levels?

microwave radiation

what are transitions in molecular vibrational levels? the bonds require more energy than microwave radiation

infrared radiation

what are transitions in electronic energy levels?

ultraviolet/visible radiation

the range of wavelengths for visible light is from?

400nm to 700nm

how do EM waves differ?

based on their wavelengths and frequencies

what is bond order?

a measurement of the number of electron pairs shared between two atoms in a chemical bond

what does bond order indicate?

the stability and strength of a bond; higher bond order = stronger and shorter bond

when do fractional bond orders appear?

in resonance structures

what is mass spectrometry?

an analytic technique used to identify unknown compounds by measuring the mass to charge ratio of ions

what is the most important information mass spectrometry reveals?

isotope distribution

what is infrared spectroscopy used for?

determines the precise structure of an atom or molecule with the use of infrared light

what are some effects that IR has on bond activity?

symmetric stretch, asymmetric stretch, symmetric bend, asymetric bend, twisting of bonds

what are wave numbers?

shows particular energies of infrared light based on their wavelengths and frequencies

what is percent transmittance?

percentage of a particular wavelength or wave number that reaches the detector

what is the region on the IR spec. beyond 1500 cm^-1

fingerprint region

what does an OH stretch represent on an IR spec.?

there is an OH group in the molecule