 Hello, my name is Kevin Conley. I'm an instructor at Foresight Tech, and I'd like to give you another installment of our lessons on nuclear chemistry. I'd like to give you a short and compact statement of the units used in nuclear chemistry. And hopefully, in your study of chemistry, you've seen the importance of units. You will likely refer back to this lecture more in the future so you can understand these units. And they come in three different categories. And some are more important than others. But I wanted to assemble them all in one place so as to avoid confusion. First of all, we have some based upon activity, which is how much radiation is going around. The next one that has to do with dose, which is how much a biological entity actually receives. And then finally, the damage that occurs, primarily the damage that will occur inside of humans. So first of all, for activity, which is how many popcorn popping do we have occurring for a nuclear activity? First of all, we have the curie. The curie has a unit abbreviation of CI. And it's based upon the number of pops or the number of decays you have during one second for one gram of radium. So if you take radium, you have one gram of it, and you wait for one second, you're going to have 3.7 times 10 to the 10 events every second. And that then is what one curie is. And the next thing is you have a becquerel, a much simpler unit, which is simply one event per second. That's going to be the rate. As you can see, if you're using radium or any other radioactive element, the becquerel probably isn't going to be a very useful unit, and the curie will. The second thing is the dose. And the dose has to do with, like any other dose that you would get of a medicine or something that is not good for you. In this case, the dose is a unit called the gray. It is, in fact, a system international unit or a metric unit. GY is the abbreviation. And the gray is simply the number of joules or the amount of energy. It could be in calories, for example. The number of joules per kilogram of body tissue that is, in fact, received. And this is also over time. In other words, as time goes by, the dosage will increase more and more. And that is factored into the dose. In other words, one hour will give you so many grays, two hours more grays, and 10 hours yet more. The next thing we get onto is probably the reason why we're mostly concerned is the damage. And the damage occurs in this case through the radiation equivalent in humans, or the REM, a term that we're probably very familiar with. The REM equals the dose, which is expressed in grays, times the particle factor. The particle factor has to do with what type of radiation we're dealing with. As was mentioned in the previous lecture, we have four types of radiation primarily, alpha, beta, gamma, and also positron. Positron is really rather rare when it comes to health effects. So what I've written down here is that the damage in REMs is equal to the dose, which is given by the grays, again, which is an overtime effect, one hour, two hour, 10 hours. This will be an increasing factor, times the particle factor, which just depends upon what type of radiation is being discussed. Gamma is the strongest. And we'll learn about why in a future lecture. Beta is second strongest. Those are electrons. And then the third strongest will be the alpha particles. And finally, the unit of damage, which is a system international, or a metric unit, is the C-vert, and that's given by SV. I'll see you in the next lecture.