Atomic Spectroscopy
Laboratory
Science & Engineering Magnet High
Mr. Puckett
Atomic Emission Spectroscopy
Laboratory
• Problem: How much energy is contained in the
quanta between the different levels of excited
electron energy orbitals? And what are the
frequencies and wavelengths of the energy?
• Hypothesis: The amount of energy given off is
calculated by the colors of the quanta of light
given off when the electrons “cascade” from upper
energy levels to the natural ground state.
Introduction and theory
• Atomic Spectroscopy is the analytical
measurement of the quantum energy level jumps
of different electron energy states.
• It is a spectral analysis of the colors (frequencies
or wavelengths) that an atom gives off when it
changes energy levels.
• Formulas: c = f and 1/  = R(1/nf2 –1/ni2) where
R = 1.097 x107 m-1 and n is the orbital of the
energy state.
• The shortcut formula is E = Ef – Ei = E2 – E1
where E = -13.6 eV / n2 , then E = hf.
Atomic Emission Spectroscopy
• In this technique, the atoms are heated up to the
point that the thermal energy promotes the
electron up to an excited energy level and then
measures the color (wavelength) of light that is
given off when the electron collapses back into
the ground state. You are looking into the atom
Einstein proposes Quanta
Energy Levels of Electrons
• Einstein also proposed that electrons,
besides emitting electromagnetic radiation
in quanta, also absorb it in quanta.
• Einstein's work demonstrated that
electromagnetic radiation has the
characteristics of both a wave--because
the fields of which it is composed rise and
fall in strength--and a particle--because
the energy is contained in separate
"packets." These packets were later called
Energy Orbitals of the Electrons
• Electron
energy
orbitals are
the regions
where there is
the greatest
chance to find
them as
clouds
Photon Energy Emitted out of
the Excited Level Electrons
• When the electron
absorbs the energy, it is
promoted to the higher
energy orbital.
• Nature wants the electron
to go back to the ground
state level (stability and
entropy reasons) and give
the energy back off at
frequencies that are
unique for that atom at
that level of energy.
Materials and Procedures
• Materials:
– 1. A hand held spectrometer.
– 2. A Fluorescence gas element tube with
Hydrogen.
• Procedures:
– 1. Turn the tube on to glow with lights reduced
– 2. View the light through the spectrometer
– 3. Record the emission lines as 102 nm.
Emission Spectroscopy Examples
Energy Level Transitions of Electrons
Energy Levels Chart Example
• Notice
the many
different
pathways
photon
energy
release
can take
back to
ground
state.
Results:
• The results are a combination of measured
visual colored spectral lines and the
calculated energy levels for the electrons.
Orbital Energy for the Atomic
Hydrogen Spectroscopy
Frequency and Wavelength of
Emitted Photons
Error Analysis:
• The main source of error in this experiment is the
angle of the spectrometer in relation to the light
tube. This angle can produce numerical results
that vary as much as 100 nm. Over a hydrogen
spectrum at 410 nm this would be 100/410 x
100% = 24.4 % error down to 16% at 656nm.
• To correct the error a computerized spectrometer
could be used to obtain more accuracy.
What YOU Learned in this lab
• Students will supply the answer to this.
• Should be at least half a page and be a
synopsis of the experimental theory and
results with quantification.