First of all, we all learned in science class that everything is made up of atoms, and that atoms are the most basic building blocks of matter. In fact, the greek root for the word atom means indivisible. Well, what we learned was actually wrong; we've now identified more sub atomic particles than atomic particles, and we theorize the existence of many more, but for our purposes, all we really need to talk about is the atom, and the three particles that make it up: the proton, the neutron, and the electron.
The proton is a positively charged particle that has a mass of 1 Atomic Mass Unit (amu). (Roughly 1.66x10
The neutron has no charge, and also has a mass of 1 amu. When the number of neutrons changes, but the number of protons remains the same, then we have different isotopes of the element. For example, the most abundant form of carbon has 6 protons and 6 neutrons. If two more neutrons are added to the nucleus, then we're dealing with the isotope Carbon-14, a radioactive isotope useful in dating old objects.
Protons and neutrons together make up the nucleus of the atom.
Electrons have a very, very small mass when compared to the proton and neutron, so we usually assume it is zero. It has a negative charge and it flies around the nucleus within a certain distance. That distance is determined by the energy level of the electron, and is a property of the electron we'll discuss in more detail later on. For now, realize that the electron does not orbit the nucleus like a planet, but instead is always within a certain range of the nucleus. An atom normally has the same number of electrons as it has neutrons, resulting in a neutral charge for the atom. If the atom gains or loses electrons, it acquires a negative or positive charge, and is called an ion.
So, the atom has electrons circling a nucleus which is made up of protons and neutrons. So, I have a question for you. What happens when you take two magnets, and hold the same poles together?
They fly apart, right? Well, particles with the same charge do the same thing. When you group a bunch of particles with the same charge together, they try to fly apart.
So, what is holding the nucleus together? It's a bundle of particles with the same charge and particles with no charge. It should fly apart all by itself.
It doesn't because there's another force at work, the nuclear force. (Actually, there are two forces, the strong and the weak nuclear forces, but that's beyond the scope of this post.) The nuclear force acts to hold the nucleus together, and is stronger than the electrostatic repulsion of the similar charges. When an atom splits, the energy that held the nucleus together, the binding energy, is released and that is the energy we call radiation.
The next question is how does this atom split, and that's what we'll address in the next post.