EM Radiation + Atomic Spectra Flashcards
Why is electromagnetic radiation said to have a dual nature?
It can be described as a wave because it has wavelength and frequency but it can also be described as a particle
When electromagnetic radiation is absorbed or emitted by matter it behaves like a stream of particles. What are these particles called?
Photons
How does the quantised energy carried by a photon relate to the frequency of the radiation?
Proportional (higher energy = higher frequency)
How does the quantised energy carried by a photon relate to the wavelength of the radiation?
Inversely proportional (higher energy = lower wavelength)
The energy associated with a single photon is given by what relationship?
E = hf OR E = hc/λ
The energy associated with one mole of photons is given by what relationship?
E = Lhf OR E = Lhc/λ
What happens when an electron in an atom absorbs a photon?
It is promoted to a higher energy level
What happens when an electron in an atom emits a photon?
It falls back down to a lower energy level
The light energy emitted by an atom produces a spectrum that is made up of a series of lines at discrete (quantised) energy levels. What is this evidence for?
The existence of various different energy levels within atoms
Describe absorption spectroscopy.
Electromagnetic radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels.
How is an absorption spectrum produced?
An absorption spectrum is produced by measuring how the intensity of absorbed light varies with wavelength.
Describe emission spectroscopy.
In emission spectroscopy, high temperatures are used to excite the electrons within atoms. As the electrons drop to lower energy levels, photons are emitted.
How is an emission spectrum produced?
An emission spectrum of a sample is produced by measuring the intensity of light emitted at different wavelengths.
In atomic spectroscopy what is the concentration of an element within a sample related to?
The intensity of light emitted or absorbed
