Hey guys, Spencer here.
Quantum mechanics in chemistry has become
an important part of the atomic models we
use today, especially in determining the position
of particles within atoms.
One of its key principles is wave-particle
duality.
This is the idea that elementary particles,
such as an electron, can behave like particles,
being at a single point - while also exhibiting
properties of waves and spreading out like
sound.
But how exactly does this concept work, and
why does it matter to us?
What is wave-particle duality?
The origin of wave-particle duality traces
back to Albert Einstein in 1905.
He discovered that through the photoelectric
effect, light was not only a wave, as previously
thought of, but also as a stream of particles
called photons.
The theory has been proven to work for particles
of matter as well.
In the classic double-slit experiment, a stream
of electrons is fired at a wall with two slits
in it.
Traditionally, one might expect the particles
to travel in a straight line.
However, when scientists performed this experiment,
the electrons actually landed mostly in several
distinct groups through the two slits, forming
a line-like pattern.
This proved that particles had wave-like behaviors
and properties, just like the diffraction
and interference of waves around the two slits.
Particle positioning depends on probability,
and electrons are said to take all possible
paths in the experiment.
The idea of particles coexisting and behaving
like waves is essential in understanding quantum
chemistry.
The discovery of wave-particle duality also
improved upon the atomic model.
In 1911, British scientist Ernest Rutherford
used his gold-foil experiment to show that
atoms contained a central nucleus and electrons
scattered outside it, similar to how the planets
orbit the sun.
However, the major problem of this model was
that the orbit of electrons would eventually
decay and crash into the nucleus according
to classical mechanics.
[EXPLOSION] Danish scientist Niels Bohr improved
upon this in 1913 using different energy levels
for electrons, using quantum energy changes
to adjust for the imbalance.
There was still the newly discovered wave-particle
duality to be considered, though.
Electrons are like waves, so that they cannot
be confined to a single point, just as a photon
can't be a single point in a light wave.
This led theoretical scientist Werner Heisenberg
to develop his uncertainty principle in 1927.
It stated that the more is known about a particle's
momentum, the less is known about a particle's
position in 3D space, and vice versa.
Therefore, there are no fixed orbits around
the nucleus of an atom, since we cannot know
the position of an electron at any given time.
Rather, modern-day atomic models use an electron
cloud to estimate the probability of an electron
being at a certain position.
Electron shells are still likely to contain
the correct amount of electrons.
It's just not guaranteed according to the
laws of quantum theory.
But if all atoms could actually be waves of
energy, and everything on Earth is made up
of atoms, what would that mean for us?
Could we simply change into a wave so that
we are everywhere at the same time or so that
we could walk through walls?
The truth is, wavelengths of particles happen
to be very small, even at the subatomic level.
French scientist Louis de Broglie derived
the equation for the wavelength of a particle
from Einstein's matter and energy equation,
energy equals mass times the speed of light
squared.
He substituted energy for Planck's constant
and the speed of light for velocity.
The end result shows that wavelength is equal
to Planck's constant divided by the product
of a particle's mass and velocity.
This is inversely proportional to wavelength,
so that the faster an object is moving and
the larger it is, the shorter its wavelength
will be.
To put this into perspective, if an average
man with a mass of 62 kilograms or 137 pounds
was walking at a pace of 1.4 meters per second,
his wavelength would be approximately 7.636
multiplied by 10 to the -39 power meters long.
That's even shorter that the diameter of a
quark , the elementary building block of matter.
So, it can be safe to say that the existence
of wave-particle duality wouldn't cause any
unexpected results for us in the future.
However, the idea that a particle can behave
like a wave on the subatomic level has changed
the field of chemistry.
The atomic model can only be accurately described
by quantum theory, while wave-particle duality
can lead to more observations on experiments,
such as spectroscopy of the elements, states
of atoms, and molecular bonds.
The principle forms the basis of what scientists
now consider the physical model of our world.
I hope you have learned something new today.
Do you have any additional questions about
wave particle duality?
Leave your thoughts in the comments below
and tell me if there are any other science
topics you would like me to cover.
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That's it for today, guys!
