1a- Electromagnetic radiation and atomic spectra Flashcards
What can electromagnetic radiation be characterised in terms of?
Wavelength and/or frequency
The different types of radiation arranged in order of wavelength is known as what?
The electromagnetic spectrum
In what unit are wavelengths of visible light usually expressed?
nanometres (nm)
Why is electromagnetic radiation said to have a dual nature?
Because it can be described as both a wave (has a wavelength and a frequency) and as a particle
When electromagnetic radiation is absorbed or emitted by matter how does it behave?
It behaves like a stream of particles. These particles are known as photons
A photon carries quantised energy proportional to what?
The frequency of the radiation
When a photon is absorbed or emitted, what happens to the electrons within the substance?
Energy is either gained or lost by the electrons
Photons in which type of radiation can transfer greater amounts of energy?
High frequency radiation
In what units is energy usually expressed?
kJ/mol
What happens to the electrons within atoms when energy is transferred to them?
The electrons 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 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.
What does the spectrum produced when light energy is emitted by an atom provide direct evidence of?
The existence of energy levels
Each element in a sample produces characteristic absorption and emission spectra, what can these spectra be used for?
To identify and quantify the element
What happens during absorption spectroscopy?
Electromagnetic radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels
