Physics Question #416

Will McAbee, a 11 year old male from Pendlton asks on November 27, 2001,

How does a atom split and how does it create such a big explosion? Also how can I split an atom at home.

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The answer

Jeremy Whitlock answered on November 27, 2001

When we say "splitting the atom" we really mean breaking the nucleus of the atom (the tiny centre part) into two or more even smaller parts. The phrase "splitting the atom" is usually applied to the splitting of uranium atoms. Uranium is an abundant mineral in the earth's crust. Its nuclei can be "split" because it has too much energy -- all it needs is a little "nudge" of extra energy to push it over the edge, and it splits into smaller pieces. This extra energy can be supplied by firing smaller particles at the uranium atom, like neutrons.

When uranium atoms are split the extra energy is released as heat. If we control this release of heat, we can generate electricity without making pollution, and this is how nuclear power works. If we don't control the heat release, that's how a nuclear explosion works (although nuclear power reactors cannot explode this way).

You can't split uranium at home (it's too complicated), but you can split another kind of atom, called "americium" (pronounced "a-mare-ee-see-um"). In fact, if you have an ionization smoke detector in your home, you're splitting it right now. Inside your smoke detector is a small amount of americium with too much energy, just like uranium. The americium gets rid of its energy by spontaneously splitting into a big chunk and a very tiny chunk. The tiny chunk is interesting because it looks just like a helium nucleus (that same gas they put in party balloons), and it flies off with enough energy to be measured by the smoke detector. If large particles enter the smoke detector, such as particles of smoke, the energy of the tiny helium chunks (actually called "alpha particles") is blocked from reaching the smoke detector's measuring device, and it sounds the alarm.

So you see, "splitting the atom" can be as destructive as a nuclear bomb, as peaceful as nuclear energy, or as simple and useful as a smoke detector in your home.

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