EM Radiation and Atomic Spectra Flashcards
Explain electromagnetic radiation: What are they? What is a common relationship used with them? What is frequency quoted in. What is the electromagnetic spectrum?
Electromagnetic radiation can be described in terms of waves and
characterised in terms of wavelength and/or frequency.
The relationship between these quantities is given by c f = λ .
Frequency is often quoted in Hz, which is the same as s-1.
The different types of radiation arranged in order of wavelength is known as the electromagnetic spectrum.
How is the energy of a photon calculated, and how can this be done for a mole of atoms releasing photons?
The energy associated with a single photon is given by:
or
E = hf
The values for the constants are h = 6·63 × 10–34 J s and
L = 6·02 × 1023 mol–1 and are given in the data booklet.
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.)
The energy associated with one mole of photons is given by:
E = Lhf or E= (Lhc)/λ
Energy is often in units of kJ mol-1 When energy is transferred to atoms, electrons within the atoms may be promoted to higher energy levels.
How are atomic emission spectra used to provide evidence of energy levels in atoms?
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.
What unit is energy given in?
KJ mol-1
What does each element produce?
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.
What is high temperatures used for in emission spectroscopy?
In emission spectroscopy, high temperatures are used to excite the electrons within atoms
When are photons emitted?
As the electrons drop to lower energy levels, photons are emitted
What is an emission spectrum?
An atom emits a photon of light energy when an excited electron
moves from a higher energy level to a lower energy level.
What does a photon carry?
A photon carries quantised energy proportional to the frequency of
radiation.
How is emission spectroscopy used to identify the quantities of elements in a sample?
An emission spectrum of a sample is produced by measuring the
intensity of light emitted at different wavelengths. In atomic spectroscopy, the concentration of an element within a
sample is related to the intensity of light emitted or absorbed.
Electromagnetic radiation can be expressed in 2 forms what are these?
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. When electromagnetic radiation is absorbed or emitted by matter it
behaves like a stream of particles. These particles are known as photons.
What happens in absorption spectroscopy?
In absorption spectroscopy, electromagnetic radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels.
