Nuclear physics and radioactivity

An atom’s nucleus is so unbelievably small that it’s difficult to imagine what it’s like. If you want to build something out of atomic nuclei large enough to be visible to the naked eye, it needs to have a diameter of ten billion nuclei. At least. Even though the atomic nucleus is so small, it carries enormous power. This power can be released in several ways -- one of them is radioactive decay.

Atomic nuclei that just decay by themselves are called radioactive. When they decay, the nucleus suddenly changes. Nuclear particles can break apart, or even leave the nucleus. When that happens, the number of protons changes. This means that afterwards we have a different atomic nucleus -- a different element.

There’s also radiation coming from the nucleus when it decays. The radiation can break other atoms and molecules apart, and upset the balance between the number of protons and electrons. And when there’s no longer the same number of electrons as the number of protons, the particle becomes positively or negatively charged. Atoms and molecules that are electrically charged are called ions. That’s why we call this kind of radiation an ionizing radiation.

Ionizing radiation damages living tissues, and can affect other materials as well. You know that atoms of the same element always have the same number of protons… and electrons. However, the number of neutrons can vary. Atoms with the same number of protons, but a different number of neutrons, are called isotopes of an element. Take carbon, an element that you find in pencils, among other things.

What we call lead in a pencil is mostly carbon. Almost all the carbon atoms in a pencil have six neutrons. Six protons and six neutrons, that makes twelve particles in the nucleus. That’s why this isotope is named carbon- 12. We write it like this.

Then there’s a tiny fraction of carbon atoms that have an extra neutron. That isotope is carbon- 13, and is written like this. It’s common among the elements that some isotopes are radioactive, while others are not. Isotopes that don’t decay are called stable. Both carbon 12 and carbon 13 are stable, but there are other isotopes of carbon that are radioactive.

The most common one is carbon 14. There’s a tiny amount of it in every living organism. We inhale it when we breathe, and plants absorb it through photosynthesis. It’s not dangerous, but actually quite useful. When an organism dies, it stops absorbing carbon 14.

And since carbon 14 atoms decay with time, the amount of carbon of that isotope slowly decreases. So, we can measure the amount of it in a piece of wood, the skin of an animal, or a mummy - and calculate how much time has passed since the material stopped absorbing carbon 14. Since it died, that is. This method is called carbon-14 dating. When we study how the nucleus of an atom is built, and how it behaves, we are involved in nuclear physics.

The foundation for nuclear physics was laid in the early 20th century. Over the last hundred years, scientists in physics and medicine have learnt more about nuclear physics. It has given us new knowledge and quite a few new inventions. Some of them are very good. Like equipment for medical examinations and treatment.

And some are not so good. Like nuclear weapons. Then there are those inventions that we may not agree upon. Like nuclear power. Those incredibly teeny tiny atomic nuclei can treat cancer, provide electricity, and spread death and destruction.

Among other things.