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Can we turn lead into gold?
Lead and gold are two metals,
and like every material, they consist of atoms.
A piece of lead, when it’s pure
is only the assembly of a large number of atoms,
all identical: atoms of lead.
Similarly, pure gold consists of a large number of atoms of gold.
So, turn lead into gold
is to transform every atom of lead into atom of gold.
We can have a simplified view of atom
imagining small particles
we call electrons which rotate around a core.
The core is made up of an agglomerate of two types of particles:
neutrons and protons.
The atom of a given chemical element is essentially
characterised by the number of protons we find in the core.
For instance, the core of an atom of lead
contains 82 protons and the atom of gold contains 79 protons.
However, the number of neutron may vary slightly.
For instance, slightly more than half of the leads
we can find in nature, corresponds to atoms
with a core that contains 126 neutrons.
As 126 neutrons plus 82 protons equals 208 particles in the core,
this is known as lead 208.
The other half of the natural lead is further divided into
two species with roughly equivalent shares:
the cores with 125 neutrons and those with 124 neutrons.
By adding the 82 protons, we have then lead 207 and lead 206.
Each of these species is called an isotope
and the lead has three different isotopes.
However, gold has only one natural isotope
with a core containing 118 neutrons plus 79 protons,
so it is gold 197.
To transform a substance into another,
we use essentially chemical reactions.
But in a chemical reaction, we cannot transform the atoms,
they are assembled differently.
For instance, if we adequately mix
oxygen with hydrogen, we obtain water.
But what happened?
One of the two atoms of the molecule of oxygen
is combined with two atoms of the molecule of hydrogen
to form a molecule of water, that is to say H2O.
Atoms are assembled differently, but are not transformed.
We can see that the quest of alchemists was already lost:
no chemical process can transform lead into gold.
So to transform an atom of lead into an atom of gold,
we must literally break the core
to remove protons and neutrons in excess.
To break a core of lead,
we now know that we must provide a lot of energy
as found in nuclear reactors
and particle accelerators.
So, effectively to perform this transformation is very expensive,
and the cost price of gold we get is infinitely higher than the market price.
The operation therefore loses all interest and no one tried to perform it.
However, it happens that gold is created in small quantities
in nuclear reactors or particle accelerators,
as a collateral consequence of their normal operation.
Gold is not produced from lead
because the difference between the two atoms is too important:
we must remove 3 protons and at least 6 neutrons.
However, the mercury, for example,
has only one proton more than gold
and 10% of natural mercury has 118 neutrons, just like gold.
However, it exists in Tennessee in United States,
a complex of the U.S. Department of Energy,
the National Laboratory of Oak Ridge,
which possesses one of the most powerful sources of neutrons in the world.
The principle of this instrument is just bombarding mercury with protons
in order to extract neutrons with very high energy.
During the collision between the protons and the cores of the mercury,
many things happen:
some protons are captured by a core and, on the contrary,
some cores break emitting protons and neutrons.
In the end, some atoms of mercury are transformed into atoms of gold,
but the quantity is too small to be usable...
Production: UNISCIEL/UNIVERSITE OF LILLE 1
Maxime Beaugeois, Damien Deltombe and Daniel Hennequin
Editing/Special Effects: Perrine Lefrileux
Music: Sébastien Ride, "Thunder Chacha" (SR Music)
Presentation: Maxime and Nina Beaugeois
Graphic design/ credits animation: Michaël Mensier