Half-Life _ GCSE Physics

When a radioactive atom goes through alpha or beta decay, the atom itself changes into a different element. For example, carbon-14 decays to nitrogen-14 when it emits beta radiation. It’s impossible to predict when an individual atom might decay because it’s completely random. What you can do is measure the time it takes for half the atoms in a radioactive substance to decay. We call this a half-life. We can use graphs to find out the half-life of a radioactive substance. All we have to do is measure the count rate over time and plot the decay curve. As you can see the count rate drops from 100 to 50 in 2 days, from 50 to 25 in another 2 days, to 12.5 and so on. Alpha and beta decay can be represented through nuclear equations. An alpha particle consists of two protons and two neutrons, this means that the mass number on an atom would decrease by 4 and the atomic number by 2. For example, radon-219 would decay into polonium-215 and emit an alpha particle in the process. This is represented in an equation like this. In beta decay, a neutron changes into a proton and a high-energy electron is released. The nucleus now has one less neutron but one more proton, so the mass number stays the same but the atomic number increases by 1. For example, thorium-234 decays into protactinium-234 and a beta particle is released. As you can see the beta particle has a -1 as its atomic number to represent the additional proton that was added. Seems a little counter intuitive but that’s just the way it is.