Electromagnetic radiation and atomic spectra Flashcards
What does Dual Nature mean?
Electromagnetic radiation can be described as a wave (has a wavelength and frequency), and as a particle.
What does electromagnetic radiation behave like when absorbed or emitted?
A stream of particles (photons)
Photons in terms of energy and frequency of radiation
A photon carries quantised energy proportional to the frequency of radiation.
When a photon is absorbed or emitted…..
energy is gained or lost by electrons within the
substance.
The energy associated with a single photon is given by:
E=hf of E=hc/λ
The energy associated with one mole of photons is given by:
E=Lhf or E=Lhc/λ
What happens when energy is transferred to atoms,
electrons within the atoms may be promoted to
higher energy levels.
An atom emits a photon of light energy when
an excited electron moves from a higher
energy level 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. This provides direct evidence for the existence
of these energy levels.
What happens in absorption spectroscopy?
Electromagnetic radiation is directed at an atomised sample.
Radiation is absorbed as electrons are promoted to higher energy levels.
What happens in emission spectroscopy?
high temperatures are used to excite the electrons within atoms.
As the electrons drop to lower energy levels, photons are emitted.
An absorption spectrum is produced by
measuring how the intensity of absorbed light
varies with wavelength.
An emission spectrum of a sample is produced by
measuring the intensity of light emitted
at different wavelengths.
In atomic spectroscopy, the concentration of an element within a sample is related to
the intensity of light emitted or absorbed.
