MadSci Network: Physics

Re: Can scientist create atoms or is it impossible to be manmade???

Date: Tue May 2 19:44:47 2000
Posted By: David Richardson, Post-doc/Fellow, Physics, Williams College
Area of science: Physics
ID: 956016711.Ph

The fast and simple answer is yes, scientists can create and destroy
atoms.  But they don't. The actual explanation of how and why they don't
will take a little longer, and I'll start below by just descibing an atom.

An atom is made up of a nucleus, which is made up of positively charged protons and no charged neutrons, and negatively charged electrons that orbit the nucleus. [In an earlier reply (949456667.Ph) I explain how scientists know that the atom is the way it is.] The type of element of an atom is defined by how many protons it has. Each different element has a different number of protons. (Hydrogen has one proton, Helium has 2 protons etc.) In neutral atoms, the number of electrons equal the number of protons. The negative charges cancel the positive charges and make the atom neutral. (An element stays the same even though it may have a different number of neutrons. The number of protons say what the element is, the number of neutrons determines which "isotope" of the element it is. I'll mention these later.)

Now before I get on to creating atoms from scratch, I'd like to go through a sort of intermediate step. This step is changing atoms from one element to another. This isn't quite like the Alchemy of Medieval times. Elements change from one to another all of the time in nature. The process nature uses is Radioactivity.

There are three types of radioactivity, only two of which cause the number of protons in the nucleus to change. These two are: alpha-decay and beta-decay.

Alpha Decay: This decay is defined by a helium nucleus (no electrons) being thrown out of the nucleus that is decaying. The helium nucleus is also known as an alpha-particle. When the helium nucleus is ejected, the nucleus that it is thrown out of has lost 2 protons and 2 neutrons. Thus, the element has changed.

As an example, let's think of Uranium, a well-known element. Let us pick one specific isotope of this element, say Uranium-235. (Uranium-238 is the most abundant of the Uranium isotopes in nature.) Uranium-235 has 92 protons and 143 neutrons, and is radioactive, emitting an alpha-particle. Because it does this, it becomes a different element. It changes to Thorium-231, which has 90 protons and 141 neutrons. There atom is no longer Uranium and so any balancing equation would look something like this:

U -> Th + He(2+)

Beta Decay: This type of decay is caused by a neutron in the nucleus turning in to a proton and an electron. The electron is shot out of the nucleus, and is called a beta-particle. The nucleus that emits the electron now has an extra proton and one less neutron and so again, the element has changed.

(The other form of radiation, gamma-rays, are actually just high energy photons, that is higher energy versions of the particles that carry normal light. All they do is remove energy from a nucleus to try to make it more stable.)

(The form of chemistry that looks at reactions with radioactive sorts of elements is called Radio-chemistry.)

Scientists regularly use other methods for changing one atom into another atom (one element into another element.) Nuclear fission (the thing that made the nuclear bomb that was dropped on Hiroshima and Nagasaki in World War 2 work) causes a nucleus to split in to two pieces of roughly the same size. Nuclear fusion joins together two atoms to make a single atom. There are other methods such as spallation in which a high speed nucleus hits another nucleus and a chunk is knocked out of the nucleus that wasn't moving, much like a car hitting a wall and knocking some bricks out of it.

So I've described ways in which atoms can change from one element to another. Now I'll get to answering your exact question: Can scientists create and destroy atoms?

As I said above, they can create them. The reason I haven't been able to find any experiments that actually create atoms from scratch is that 1) Why bother when you can get pretty much any atom you want by using atoms that already exist, either by natural radioactive decay or by other means, 2) The energy needed to create even a small atom is huge.

Let me explain how an atom could be created. You may already have heard of Einsteins famous equation:


This means that energy is equivalent to mass and vice versa. This means if you have enough energy, you can create something with mass, like a particle. The more energy you have, the heavier the particle can be.

A common example of this equation in effect is a process called Pair Production. In this process, a gamma-ray (remember, that is a high energy particle of light) becomes an electron and an anti-electron (a positron). The positron is the same as an electron in every way except it has a positive charge, not a negative charge like the electron. A positron is what is known as a piece of anti-matter. This process starts out with energy (the photon, which has no mass) and becomes two things with mass, the electron and positron.

The opposite effect is called Pair Annihilation. The positron and electron collide and produce at least 2 photons. Mass becomes energy.

From this you can see that if we could get enough energy we could produce any particle we wished. However, to produce a whole proton, we would need to have a photon with an energy over 1800 times larger than needed for the pair production. The heavier the particle you produce the more energy you need.

It's difficult to explain how much energy this is, but it is actually a very large amount. If we think of the energy of the light coming from a normal lamp bulb as being 1 unit of energy. The energy needed for pair production, to produce an electron and a positron, is about 1 million (1000,000) units of energy (you would need one billion normal light photons to produce just one pair production photon.) So to produce a proton and anti-proton you'd need about 1 billion (1000,000,000) units of energy.

And controlling such high energy photons is difficult too. So you can see that producing even just a hydrogen atom woulf take a lot of work. Much more work than just getting it from somewhere on the Earth, like from the atmosphere.

There is one example of a whole atom being produced, but it is not of normal matter. It's actually made out of the anti-matter that I mentioned earlier. In the last couple of years, it has been possible to produce anti-Hydrogen. This is the same as normal hydrogen (one proton and one electron) but made of anti-matter, so instead of a proton there is an anti-proton (negative charge), and instead of an electron there is a positron (positive charge).

Anti-matter is difficult to work with because as soon as it hits normal matter it annihilates (disappears into photons as I mentioned above). So only a few of these atoms have ever been made. It is an extremely difficult experiment to perform, and that we have seen any anti-hydrogen produced is a major success.

However, it is proof that scientists can make atoms.

So, to summarise my rambling: Scientists can make atoms, but they don't because it's a lot more difficult than just getting them from somewhere on the earth. Scientists can also change atoms from one element to another, by the methods I mentioned above.

I hope that this has explained everything in a clear enough way for you. If you have any questions at all, feel free to email me at: . And if anyone knows of experiments that actually created normal matter atoms, if you could email me also, so that i can correct this account.

Thanks for your question Keith.

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