Atomic Emission Spectroscopy
Chapter 20 (see also 2-10, 5-3)
What happens when an atom absorbs energy?
The electrons in an atom can be excited from the ground state:
An atom with an electron in an excited state is
So it will return to the ground state by
Each electron in each atom has a very specific amount of energy that it will
absorb and emit. We say it is
Light:
Examples:
Analytical chemists use the phenomenon of atomic emission to measure
amounts of
How it works:
Instrument components:
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Sample preparation: see section 2-10, p.46-47
Data analysis:
When using atomic emission spectroscopy,
Molecular Spectroscopy
Chapter 19, sections 4 and 5
What happens when a molecule absorbs energy?
For comparison, let’s remember what happens when an atom absorbs energy:
An atom is not going to
What happens when a molecule absorbs light is very different, and depends on
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UV/VIS spectroscopy of molecules
A molecule can experience
Molecular Orbitals:
Different electronic transitions involve the absorption of different wavelengths of
energy, but they are not discrete wavelengths.
UV spectrum of aspirin
Spectrophotometry
We use the Spec 20 to measure
A=
By measuring %T for a series of standards, we get a calibration curve:
The line equation for this curve:
Complementary colors
Chapter 18 # 8, 10, 14, 15, 16, 20
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