chemistry - 1.1 Flashcards
How can electromagnetic radiation be described?
In terms of waves and characterised in terms of wavelength and/or frequency.
What is the relationship between wavelength, frequency and speed of light?
c = f lambda
What is known as the electromagnetic spectrum?
The different types of radiation arranged in order of wavelength.
What are wavelengths of visible light normally expressed in?
Nanometres.
What can electromagnetic radiation be described as?
A wave (has a wavelength and frequency), and as a particle, and is said to have a dual nature.
When electromagnetic radiation is absorbed or emitted by matter, what does it behave like?
A stream of particles - known as photons.
What does a photon carry?
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.
What can photons in high frequency radiation transfer?
Greater amounts of energy than photons in low frequency radiation.
The energy associated with a single photon is given by:
What is the energy associated with a single photon given by?
E=hf or E=hc/lambda
What is the energy associated with one mole of photons given by?
E=Lhf o rE=Lhc / lambda
What units is energy often given in?
kJ mol-1
When energy is transferred to atoms, what may happen to electrons within the atoms?
They may be promoted to higher energy levels.
When does an atom emit a photon of light energy?
When an excited electron moves from a higher energy level to a lower energy level.
What does the light energy emitted by an atom produce?
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 does each element in a sample produce and what can these be used for?
Characteristic absorption and emission spectra. These spectra can be used to identify and quantify the element.
In absorption spectroscopy, what is electromagnetic radiation directed at?
An atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels.
How is an absorption spectrum produced?
By measuring how the intensity of absorbed light varies with wavelength.
In emission spectroscopy, what is used to excite the electrons within atoms?
High temperatures.
As the electrons drop to lower energy levels, what happens?
Photons are emitted.
How is an emission spectrum of a sample 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.
