5. Radioactive decay

Radioactive decay types article

What are nuclear reactions?

Sometimes atoms aren’t happy just being themselves; they suddenly change into completely different atoms, without any warning. This mysterious transformation of one type of element into another is the basis of nuclear reactions, which cause one nucleus to change into a different nucleus. Just like chemical reactions cause compounds to turn into other compounds by swapping their electrons, nuclear reactions happen when the number of protons and neutrons in the nucleus of an atom change.

Some types of nuclear reactions can actually kick protons out of the nucleus, or convert them into neutrons. Since we know what to call an element by looking up its number on a periodic table and then reading off its name, when the atomic number (number of protons) changes, so does the name of the element. This makes nuclear reactions look somewhat like alchemy: an atom of potassium (atomic number 19) can suddenly and unexpectedly transform into an atom calcium (atomic number 20).

The only sign that anything has changed is the release of radiation, which we’ll talk more about in a little bit.Even more strangely, nuclear reactions often occur almost entirely randomly. If you have a single nucleus that you are certain will eventually decay into a different nucleus, you still have only a rough idea how long it will take for you to see it happen. You could be sitting watching the nucleus for anywhere between a few seconds to your entire lifetime, and at some point it would suddenly decay without any warning! However, depending on the type of nucleus, you can predict how long on average it would take to decay if you watched many nuclei at once.

So while the average time to decay is a measurable number (for potassium it’s over a billion years), the exact time of the decay is entirely random.There are three types of nuclear reaction, each of which cause the nucleus to shoot out a different, fast-moving particle (like a photon or electron). These released particles are a side effect of the element changing its atomic number or mass, and they are what scientists generally mean when they warn about nuclear radiation, since fast-moving particles can act like tiny bullets that poke holes in your body. However, much nuclear radiation is actually harmless, and it occasionally can be harnessed to provide new type of medical or diagnostic tools.

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