Electromagnetic radiation and atomic spectra Flashcards
What is wave number?
The number of waves per cm of radiation.
EM radiation can be described as?
A wave and as a particle, and is said to have a dual nature.
What is the EM spectrum?
Different types of radiation arranged in order of wavelength.
When EM radiation is absorbed or emitted by matter it behaves like …
A stream of particles, known as photons.
What is a photon?
Carried 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 is the difference in energy transfer of photons in high frequency and low frequency radiation?
Photons in high frequency radiation can transfer greater amounts of energy.
The energy associated with a single photon is given by: (2 formulas)
E=hf or E=hc/λ
The energy associated with 1 mole of photons is given by: (2 formulas)
E= Lhc/λ or E=Lhf
What happens when energy is transferred to atoms?
Electrons within the atoms 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.
Each element in a sample produces characteristic absorption and emission spectra. These spectra can be used to?
Identify and quantify the element.
What is absorption spectroscopy?
EM radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels.
How is absorption spectrum produced?
By measuring how the intensity of absorbed light varies with λ.
What is emission spectroscopy?
High temperatures are used to excite electrons within atoms. As the electrons drop to lower energy levels, photons are emitted.
How is an emission spectrum of a sample produced?
By measuring the intensity of light emitted at different λ.
In atomic spectroscopy what is the concentration of an element within a sample related to?
The intensity of light emitted or absorbed.
Energy associated with a single photon is given by: (2 formulas)
E=hf or E=hc/λ
The energy associated with 1 mole of photons is given by: (2 formulas)
E=Lhc/λ or E=Lhf
What is energy often given in?
Units of kJ mol-1
What happens when energy is transferred to atoms?
Electrons within the atom 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 provides direct evidence for the existence of these energy levels?
The light energy emitted by an atom produces a spectrum that is made up of a series of lines at discrete (quantised) energy levels.
Each element in a sample produces characteristic absorption and emission spectra. These spectra can be used to?
Identify and quantify the element.
