Alright, so now that we've covered the basics of the atom, in this video we're going to introduce isotopes and so all atoms of the same element are going to have the same number of protons and that's because if you change the number of protons then by definition you're going to change the element. And so once again all atoms of the same element will have the same number of protons. However, all atoms of the same element do not necessarily have the same number of neutrons, and so the number of neutrons can vary between atoms of the same element. And this is exactly what leads us to this idea of isotopes. And so isotopes are defined as atoms of the same element that only vary in the number of neutrons and so isotopes are always, once again, going to have the same atomic numbers, and that means that they're gonna have the same number of protons. And once again, that's because if you change the atomic number or the number of protons, you're going to change the element. And so all isotopes will have the same number, same atomic number, or the same number of protons. But once again, they do not have the same number of neutrons. So that means that they will have different mass numbers, which we're called the mass number is the total number of protons and neutrons. And the reason they have different mass numbers is because they have different neutrons. And so if you have varying number of neutrons then you're automatically going to vary in the mass number. Now recall from our previous lesson videos that not only did we define atomic number and mass number, but we also defined the atomic mass which is very similar to the mass number but it's different in the fact that it is going to be the average mass of all of the isotopes that exist for a particular, element. And so let's take a look at our example down below to look at the atomic mass of carbon's 3 isotopes. And so you can see that we're showing you the 3 isotopes of the carbon atom down below. The first one is here, the second one is here, and the third one is right here. Now one thing to note about these 3 isotopes of carbon is that they all have the same exact number of protons. They all have 6 protons, and that is once again going to be the atomic number. So they all have the same atomic number and the same number of protons as we indicated up above. Now also notice that all three of these scenarios right here also have the same exact number of electrons. The electrons also does not vary between these three scenarios, And so, really, the only thing that differs between these three scenarios is going to be the total number of neutrons, which we have here in the middle. Notice that when you count up the number of neutrons in the nucleus of this first one there are a total of 6 neutrons, when you count up the neutrons here there are a total of 7 neutrons. And when you count up the neutrons here, there are a total of 8 neutrons. And so once again, these three scenarios right here only differ from each other in the total number of neutrons in the nucleus, and that is what makes them isotopes, atoms of the same element that only vary in the number of neutrons. Now if we wanted to calculate the mass number for each of these three scenarios, then we need to total up the total number of protons and the total number of neutrons. But once again, the total number of neutrons is going to vary, which means that the mass number will also vary for each of these isotopes. So, if we wanna determine the mass number for this first atom, we take the total number of protons, which is 6, and add that to the total number of neutrons, which is also 6, and that gives us a mass number of 12. And so this is referred to as a carbon 12 atom, and once again, it can be abbreviated as this right here where the 12 indicates the mass number and the 6 indicates the atomic number or the number of protons, which does not change in all of these scenarios. Now if we wanna calculate the mass number of the second isotope, once again, take total number of protons, add the number of neutrons, so 6 plus 7, that gives us 13. So this isotope here is carbon 13. And so, once again, we can put the 13 up above right here to indicate its mass number. And then, if we wanted to do the same and calculate the mass number for this last, isotope over here, all we need to do is sum up the total number of protons, which is 6, plus the number of neutrons which is 8, 6 +8 is 14. So this is a carbon 14 atom. And so, what you'll also notice is that these 3 isotopes can also differ in the abundance. And so, notice that this first isotope over here makes up the vast majority of all carbon atoms. In fact, it makes up about 99% of all carbon atoms, and only a small portion of all carbon atoms are made up of these other isotopes. In fact, only 1% of all carbon atoms are made up of these other 2 isotopes. And so the mass of these other isotopes, is going to have a very small impact on the average mass of all of the isotopes. And remember, the average mass of all of the isotopes is going to be the atomic mass, which is different than the mass numbers that we just calculated here. These numbers that you see here are the mass numbers and the atomic mass is once again going to be the average mass of all of the isotopes. So the atomic mass, we are showing you over here. Considering a 100% of these carbon atoms, we have to take the average. And once again, because 99% of all of the carbon atoms are carbon 12, the average is gonna be really, really close to, the mass number of the most abundant isotope. And so that's why it's 12.011. The 0.011 is coming from the small tiny percentage of isotopes that are slightly heavier than 12. And so this here concludes our introduction introduction to isotopes and we'll be able to get some practice as we move along through our course. So I'll see you all in our next video.
2
Problem
Problem
What is TRUE about carbon-13 and carbon-14?
A
They are isotopes.
B
They have the same mass number.
C
They have the same number of neutrons in their nuclei.
D
They behave differently in biological reactions.
E
None of the above are true.
3
Problem
Problem
How are Carbon-13 and Nitrogen-15 respectively different from the more abundant isotopes Carbon-12 and Nitrogen-14? Carbon-13 and Nitrogen-15 _______________:
A
Each have an extra neutron.
B
Each have an extra proton.
C
Each have one less neutron.
D
Each have one less proton.
E
Each have one less electron.
4
Problem
Problem
The atomic number of nitrogen is 7. Nitrogen-15 has a greater mass number than nitrogen-14 because the atomic nucleus of nitrogen-15 contains ________.
A
7 neutrons.
B
8 neutrons.
C
8 protons.
D
15 protons.
5
concept
Radioactive Isotopes
Video duration:
3m
Play a video:
Video transcript
Alright, so now that we've introduced isotopes in this video, we're going to talk a little bit about radioactive isotopes. And so radioactive isotopes are really just defined as isotopes themselves that are really, really unstable and break down over periods of time by emitting energy in the form of rays or particles. And so if we take a look at our image down below over here on the left hand side, notice that we're showing you an example of the radioactivity of a carbon 14 isotope. And so this here represents the nucleus of the radioactive atom, more specifically, the nucleus of the carbon 14 isotope, which we know from our last lesson video is going to have a total of 6 protons in its nucleus and a total of 8 neutrons in its nucleus since its mass number is 14. Now carbon 14 is a radioactive isotope, meaning that it is really really unstable and will break down over time by emitting energy in the form of razor particles. And so this arrow right here represents released energy, and this arrow down here represents released subatomic particles. And so once again, this radioactive atom is going to decay and break down over time. Now the rate that radioactive atoms break down is pretty consistent, and so from that consistency, scientists can calculate what's known as the half life, and the half life is defined as the exact amount of time it takes for exactly half of all radioactive atoms in a sample to break down. And so these radioactive isotopes actually have several important uses in human life, and so for example radioactive isotopes are used in medicine such as, for giving MRIs, and they can be used in other fields of medicine as well. So they're very, very important, for that aspect, But radioactive iso isotopes can also be used for what's known as radiometric dating of fossils. And this is basically how scientists can determine how old dinosaur bones are, by just looking at the amount of radioactive isotopes that are present in the, fossils and then using the half life to calculate or approximate approximately how old the fossils are. Now we're not gonna talk about that exact process but you should be aware in your biology course that radioactive isotopes will break down over time. They can have a half life which is the time it takes for half of it to break down, and, they can be used in medicine and for radiometric dating of fossils. And so this here concludes our lesson on radioactive isotopes, and we'll be able to get a little bit of practice in our next few videos, so I'll see you all there.
6
Problem
Problem
Radioactive isotopes are utilized for all of the following except:
A
Dating fossilized material of once living things.
B
Radiation treatment to slow or stop the development of cancer cells.
C
Labeling regions of the body with radioactivity for special imaging techniques.
D
All of the above.
7
Problem
Problem
The isotope Carbon-14 has a half-life of 5,730 years. How many years must pass for a sample of Carbon-14 to break down to ¼ of its original amount?