SUMMER 2023

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THE DISTRIBUTOR’S LINK
ROB LaPOINTE FASTENER SCIENCE SPECTROSCOPY – THE ELEMENTAL CODE BEHIND THE CHEMISTRY OF METAL from page 90
FIGURE 7. THE EMISSION SPECTRUM OF SODIUM.
FIGURE 5. A QUANTUM MODEL OF ELECTRON EMISSION.
As an electron transitions between a higher level like
n=4, to a lower level like n=1, it must release some of
the energy that it has at n=4 so that it can reduce to
the energy that an electron has at n=1. The difference in
energy between n=4 and n=1 corresponds to the energy
of a particle of light, known as a photon, which it releases.
In this example the photon is blue. Since light is a form of
energy, the transitioning electron emits a blue photon so
that it can reduce its energy by the precise amount that
allows it to exist at the n=1 level. The electron can also
make other transitions between levels that correspond to
specific energy changes and specific colors of photons.
The thing to get here is that every possible energy change
an electron can make to a lower level, corresponds to
a specific color of photon produced when it makes that
change. Interestingly, electrons can only exist at very
specific energy levels and not in-between. Because of
this, atoms of a particular element can only produce
very specific colors of light when the electrons transition
from higher levels to lower levels. Figure 6 shows us the
visible colors that hydrogen can make when electrons
transition between high energies to lower energies. The
most common transition is the one that produces a 656
nanometer (nm) photon. This is why so called “neon”
signs that use hydrogen gas in a tube produce what we
perceive as red light.
Not only does hydrogen produce a unique set of colors
when its electrons transition, but so does every element
on the periodic table. Each element produces a unique
set of colors that enable it to be identified by its emission
spectrum. Figure 7 shows the emission spectrum from
sodium. Notice the two strong yellow lines around 500
nm. They are the predominate colors coming from sodium
as they represent the most common electron transition.
Many cities use sodium vapor lamps for their streetlights
and the tell tail sign of sodium vapor is the yellowish
quality to the light (see Figure 8).
Not only do all elements have a unique emission
spectrum, but they also have a corresponding unique
absorption spectrum. When a particular element is in an
energetic environment, it will only absorb energy that is
exactly equal to the energy that its electrons can have
to jump up to a particular level. All other energies will be
ignored by the electrons as the electrons cannot exist at
all energies in an element.
Now that we understand a bit about how electron
transitions in the atom produce light, we can understand
how to determine the chemistry of a material based on the
light it produces when its electrons transition from high
energies to lower energies. If we sample a small piece of
the metal of which a fastener is made, we can put that
metal in a state of high energy.
FIGURE 6. THE EMISSION SPECTRUM OF HYDROGEN.
FIGURE 8. SODIUM VAPOR STREET LIGHTS WITH THEIR
DISTINCTIVE YELOOW COLOR.
CONTINUED ON PAGE 154