DATE ___________________
NOTES-025
CHEM 110 (BEAMER)
xNotes-25x Light By Emission
Light by Emission and Emissions Spectra
Diagram: Light by Emission
ground state electron
excitation; excited state
relaxes to ground state
incident light
ground state electron
excitation
relaxation
emitted light
Energy (in this case, light, has the
right energy to excite an electron)
The electron is “excited” and moves to a
higher energy level (the excited state).
As energy dissipates, the electron
relaxes back to the ground state.
Light is emitted.

The
ground state electrons
can be excited through radiation (light), heat, chemical reaction, or – in rare cases – a
a physical strike.
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DATE ___________________
NOTES-025
CHEM 110 (BEAMER)
Atomic Emissions Spectrum
658 nm
486 nm
Spectrum Tube (filled
with hydrogen gas)
434 nm
410 nm
Beam of Light emitted by Hydrogen
Gas is directed through a prism
Atomic Emissions Spectrum

The
Atomic Emissions Spectrum
valence electrons
are excited. The
is the set of wavelengths that are emitted from a substance when its
atomic emissions spectrum
is
unique
for every substance. Thus, a substance can be identified through its atomic emissions spectrum.
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