 Hello, my name is Kevin Conley and I'm from Foresight Tech. This is another lecture dealing with nuclear chemistry. In this case, what I would like to do is to go over writing a nuclear equation when you're given in words what the equation is. For example, if you are charged with writing the bounced equation for the beta decay of iodine 131, how would you go about doing this? Well, first of all, you know that you have iodine, which has a specific mass number of 131. And you look up in the periodic table to find iodine. And from that, you can find out that it has an atomic number of 53 protons. You also happen to know that it's a beta decay. The beta decay, of course, will have a beta particle and electron as a product. So the first step is to write the incomplete equation. You start with iodine. And as you reactant, and as a product, you're going to have a beta particle plus something else. It's our job to find out what that something else is. Second step is determine the atomic number of the missing isotope. Well, if we begin with a charge of 53 plus, and we come over here, we have to subtract the product, which is a negative 1. 53 minus a negative 1 is a 54. So on the left, we'll have 53. On the right, we'll have 54 minus 1, which is 53 as well. That conserves the charge. The next thing we need is determine the mass number of the missing isotope. In this case, we have 131 protons and neutrons on the left. We have zero protons and neutrons in the beta particle. So we still maintain 131 protons and neutrons over on the right-hand side. So we have to determine the element and the symbol. Well, if you look in the periodic table, number 54 will be xenon with a symbol of Xe. And then finally, we write the balanced equation, where we go from 131 iodine to a beta particle plus 131 xenon. And finally, you check the math. Well, let's take a look. 53 minus negative 1 is going to be 54. That looks good. And 131 minus 0 gives us 131. Take a look at this video again to make sure that you get the process. This is a rather simple example, but this procedure will always work for the alpha, beta, gamma, and positron decay reactions that you'll need to know.