Eletromagnetic Radiation And Atomic Spectra Flashcards
Describe Electromagnetic radiation
Electromagnetic radiation can be described in terms of waves and characterised in terms of wavelength and/or frequency.
Describe the relationship of frequency and wavelength in terms of an equation
The relationship between these quantities is given by c = f x(lambda)
Describe how different types of radiation are arranged
The different types of radiation arranged in order of wavelength is
known as the electromagnetic spectrum
How are wavelengths of visible light expressed
In (nm)
How can electromagnetic radiation be described in terms of waves and particales
Electromagnetic radiation can be described as a wave (has a wavelength and frequency), and as a particle, and is said to have a dual nature.
Describe what happens when electromagnetic radiation is emitted or absorbed
When electromagnetic radiation is absorbed or emitted by matter it behaves like a stream of particles. These particles are known as photons.
Describe what a photon carries
A photon carries quantised energy proportional to the frequency of radiation.
Describe what happens to a substance when a photon is absorbed or emitted
When a photon is absorbed or emitted, energy is gained or lost by electrons within the substance.
Equation of energy associated with a single photon is
The energy associated with a single photon is given by:
E=hf orE=hc/(lambda)
The energy associated with one mole of photons is given by:
The energy associated with one mole of photons is given by:
E=Lhf orE=Lhc/(lambda)
Describe what Avogadro’s constant is and its symbol
L is Avogadro’s constant and is the number of formula units in one mole of the substance. (Formula units can be atoms, molecules or groups of ions, depending on the type of bonding present.)
Describe the orientation of electrons when energy is transferred to atoms
When energy is transferred to atoms, electrons within the atoms may be promoted to higher energy levels
Describe when an atom emits a photon of light and what happens after
An atom emits a photon of light energy when an excited electron moves from a higher energy level to a lower energy level
Describe how a spectrum is produced and how this shows evidence for 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. This provides direct evidence for the existence of these energy levels.
Describe how absorption and emission spectra can be used for element
Each element in a sample produces characteristic absorption and emission spectra. These spectra can be used to identify and quantify the element.
Describe absorption spectroscopy
In absorption spectroscopy, electromagnetic radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels
How is an absorption spectra produced
An absorption spectrum is produced by measuring how the intensity of absorbed light varies with wavelength.
Describe how electrons are excited in emission spectroscopy
In emission spectroscopy, high temperatures are used to excite the electrons within atoms.
Describe what is emitted as electrons drop to lower energy levels
As the electrons drop to lower energy levels, photons are emitted.
Describe how an emission spectrum is produced
An emission spectrum of a sample is produced by measuring the intensity of light emitted at different wavelengths.
Describe how the intensity of light emitted or absorbed relates to an element sample
In atomic spectroscopy, the concentration of an element within a sample is related to the intensity of light emitted or absorbed.
