1.1 Electromagnetic Radiation and Atomic Spectra Flashcards
How can electromagnetic radiation be describes and charaterised?
- Described in terms of waves
- Characterised in terms of wavelength and or frequency
What is the relationship between wavelength and frequency?
c = fλ
What can different types of radiation arranged in order of wavelength be known as?
Electromagnetic radiation
What are wavelengths of visible light normally expressed in
nm (nanometers)
Describe the duel nature of electromagnetic radiation?
When electromagnetic radiation is absorbed or emitted by mater it can be described as a wave and as a particle
What are photons?
Particles of light emitted when electromagnetic radiation is emitted or absorbed by matter
What happens when electromagnetic radiation is absorbed or emitted by matter?
It behaves like a stream of particles called photons
What does a photon carry?
Quantised energy
Explain the energy of a photon
it is 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
Explain photons in high and low frequency radiation
- Photons in high frequency radiation can transfer greater amounts of energy
- than photons in low frequency radiation
What is the energy associated by one single photon given by?
E = hf
E = hc / λ
What is the energy associated by one mole of photons given by?
E = Lhf
E = Lhc / λ
What units are energy often in?
KJmol^-1
What happens when energy is transferred to atoms?
electrons within the atoms may be promoted to higher energy levels
When will an atom emit a photon of light ?
when an excited electron moves from a higher energy level to a lower energy level
What happens when an exited electron move from a higher energy level to a lower energy level?
A photon of light is emitted
What provides direct evidence for the existence of energy levels?
The light energy emitted by an atom produces a spectrum that is made up of a series of lines at discrete energy levels
What does each element in a sample produce?
Characteristic absorption and emission spectra
What can the characteristic absorption and emission spectra of an element be used for?
Can be used to identify and quantify the element
What happens in absorption spectroscopy?
- EM radiation is 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
What happens in emission spectroscopy?
- High temperatures are used to excited the electrons within atoms
- As the electrons drop to lower energy levels, photons are emitted
How is an emission spectrum produced?
By measuring the intensity of light emitted at different wavelengths
