inorganic chem Flashcards
a) how can electromagnetic radiation be described + characterised?
- described in terms of waves
- characterised in terms of wavelength and/ or frequency
visible light travels in…
waves
what are waves measured in?
what is the symbol?
m
λ
what is frequency?
the no. of waves which go by a fixed point in 1 second
what is frequency measured in?
what is the symbol?
f
Hz or s-1
what is the speed of light formula, showing the relationship between frequency and wavelength?
c=f x λ
what is the electromagnetic spectrum?
the different types of radiation arranged in order of wavelength
wavelength of what particular type of light is measured in nm rather than m?
visible light
describe electromagnetic radiation
-can be described as a wave (have a wavelength and frequency)
-can also be described as a particle
hence has DUAL NATURE
what is the mnemonic for the electromagnetic spectrum
Good Gamma rays Xylophones X-rays Use Ultraviolet Very Visible Interesting Infrared Musical Microwaves Rhythms Radiowaves
what is the e/m radiation wavelength range?
from 10-¹²m to 10²m
as λ increases, f …
as f increases, λ …
as λ increases, f decreases
as f increases, λ decreases
what is visible light’s range?
400-700nm
what is 1 nm equal to in m?
1nm = 10-⁹m
when electromagnetic radiation is absorbed or emitted by matter, it behaves like…?
a stream of particles a.k.a- photons
what is a photon
carries quantised energy proportional to the frequency of radiation
what happens when a photon is absorbed or emitted?
- energy is gained or lost by electrons within the substance
- the photons in high frequency radiation can transfer greater amounts of energy than photons in low frequency radiation
the energy associated with a single photon is given by the formula…
E = hf or E = hc / λ
the energy associated with a one mole of photons is given by the formula…
E = Lhf or E = Lhc / λ
what units are generally used for energy?
kJmol-¹
what happens when energy is transferred to atoms?
electrons within the atoms may be promoted to higher energy levels
give direct evidence for the existence of energy levels
the light energy emitted by an atom produces a spectrum made up of a series of lines at discrete (quantised) energy levels
absorption + emission spectra can be used to identify + quantify an element. why?
each element in a sample produces characteristic spectra.
a.k.a- each element has its own spectrum
describe absorption spectroscopy
-electromagnetic radiation is directed at an atomised sample. radiation is absorbed as electrons are
promoted to higher electrons
-an absorption spectrum is produced by measuring how the intensity of absorbed light varies with wavelength
describe emission spectroscopy
- high temperatures are used to excite the electrons with atoms. as the electrons drop to lower energy levels, photons are emitted
- an emission spectrum of a sample is produced by measuring the intensity of light emitted at different wavelengths
describe atomic spectroscopy
the concentration of an element within a sample is related to the intensity of light emitted or absorbed
what are the five steps to colorimetry?
- prepare 4 or 5 standard solutions of the chemical whose concentration you are trying to determine
- choose a filter complementary to the colour of the sample
- use a blank (solvent) first e.g- deionised water
- produce a callibration graph by inserting the standards into the device and measuring absorbance
- now place unknowns in the device and measure absorbance. use the graph to determine concentration
what is the principal quantum number? what is it’s abreviation name?
it (n) refers to the energy level e.g- n=1 is the energy level closest to the nucleus