What is Nuclear Chemistry Mr. Villegass 10 th Grade Chemistry Class Click Here To Jump In Quick Overview of Presentation Introduction What is Nuclear Chemistry? Nuclear Chemistry is the study of nuclear reactions, with an emphasis on their uses in chemistry and their effects on biological systems (Chemistry: The Central Science 10 th Edition, 2006). So, thats great and all but what does that really mean? Introduction What Is Nuclear Chemistry? In Chemistry, Nuclear refers to the atomic nucleus: the massive, positively-charged center of the atom built of protons and neutrons. Therefore, nuclear reactions" are just changes concerned with the nuclei of atoms! Nuclear Chemistry is a seriously cool, ever-growing side of chemistry, explaining abstract and complex scientific phenomena! The existence and extreme brightness of stars comes from the incredible energy released from a nuclear reaction called fusion, where Hydrogen atoms collide and combine their nuclei to form Helium atoms! Introduction What is Nuclear Chemistry? Nuclear Chemistry is a field that is expanding at an incredible rate, and by collaborating with our friends in Physics, weve made some amazing discoveries in the nitty-gritty, itty-bitty side of science!. Proceed to learn about the fundamentals of Nuclear Chemistry, give it some thought, then take the quiz to prove your newfound knowledge Go forth and discover! Learn About It! Learn About It! Types of Radioactivity! Types of Radioactivity! Radiation! Think About It! (Apply It!) Think About It! (Apply It!) Quiz! Main Menu Go to the next slide and click on the video for a quick recap on reactions! This will also help you transition into the new material! Key Vocabulary Nucleus: Center of the atom contains massive protons and neutrons. Protons and neutrons are essentially equal in mass. Protons: Determine the element. Positively charged Neutrons: Determine the isotope. Neutrally charged Isotopes: Atoms of the same element that have different numbers of neutrons (different mass numbers). Different isotopes of the same element often vary in stability, due to the number of protons (proton-neutron ratio) or due to the large number of both combined. All elements have isotopes: atoms that have the same atomic number (number of protons) but a different mass number (total number of protons and neutrons). Some isotopes occur more commonly than others, and some are more stable than others as well! The stability, like all other nuclear properties, depends on the number of protons and neutrons. A fundamental phenomenon of nature called the strong force holds the protons and neutrons together in the nucleus, but when the nucleus becomes overcrowded, the strong force is not enough to keep the nucleus together and stable! The unstable nucleus must do something to return to a low-energy state! With too much stuff in the nucleus, instability strikes! An unstable nucleus is also called a radionuclide, and by extension, isotopes with radionuclides are called radioisotopes. Radioactivity is a general term used to describe instability in an atom that is relieved by some means. When an isotope is radioactive, it must do something to relax, in a sense. But atoms cant settle down by sipping lemonade on a beach or reading a book by the firelight like we can. Instead, they must make a nuclear change to obtain a state of stability. This nuclear change is called radiation. Learn About It! Types of Radioactivity Radiation is also referred to as radioactive decay. In the process of radioactive decay, the radioisotope throws stuff away from the nucleus. After all, the stuff in the nucleus is whats causing the problem, right? There are three main types of radioactive decay: Alpha Decay An alpha particle (a) is emitted from the unstable nucleus. An alpha particle essentially a helium nucleus (two neutrons, two protons) thrown from the radionuclide. Beta Decay A beta particle (B) is emitted from the unstable nucleus. A beta particle is essentially a high-energy electron (e-) thrown from the radionuclide. Gamma Decay Gamma radiation (y) is emitted from the unstable nucleus. A gamma ray is essentially very high-energy light thrown from the radionuclide. Alpha Decay When an isotope of an element has a very large mass number ( a lot of protons and neutrons), a lot of energy is pent up excessively in the nucleus. To release this energy, an Alpha Particle may be released: An alpha particle is composed of 2 protons and 2 neutrons ( a Helium nucleus). When a-decay occurs, the isotopes element changes, becoming the element two places before it on the periodic table. Some examples can be seen on the next slide! Learn About It! Examples of Alpha Decay Learn About It! Beta Decay Early on in the periodic table, it is normal to see a stable isotope which has a proton-neutron ratio of about 1:1 (one proton for every neutron). However, as the number of protons in an atom gets very large down the periodic table, we see that isotopes are more stable when there are more neutrons than protons. Despite this, it is very possible for there to be too many neutrons, even considering the increased ratio. In this case, a neutron converts to a proton and an electron, where the proton stays bound in the nucleus, and the electron is emitted as a Beta Particle: The resulting proton changes the element and helps to balance the proton-neutron ratio. Thus, the Atomic Number increases by one, and Mass Number stays the same. Learn About It! Examples of Beta Decay Learn About It! Gamma Decay Alpha and beta decay both restore stability in the nucleus of an isotope by altering the number of protons and neutrons, but after these two types of decay, the atom is often left in an excited, energetic, unstable stable state. To further stabilize, the nucleus emits energy in the form of high-energy Gamma Rays: A gamma ray is an electromagnetic wave of very high frequency essentially, very high-energy invisible light. Learn About It! Examples of Gamma Decay Through alpha and beta decay, we see the element of an atom can change with the loss or gain of protons! When forced by human hands, this change of elements is often referred to as a transmutation. Alchemists attempted to achieve transmutation in order to change Lead (a typically common, low-worth metal) into gold (a very precious metal). Their attempts were unsuccessful, and they never achieved true transmutation, because they did not fully understand the difference between atomic and nuclear changes. All they did was change the arrangement of different elements in compounds and compounds. These combination and replacement reactions do not cause nuclear changes, as the electrons are the key components in bonding (forming compounds and molecules). No change in protons would ever result from such reactions. Learn About It! Half-Life of Isotopes One nifty rule that we have figured out about radioactive samples on a macroscopic scale is that it takes a specific amount of time for half of the samples radioactive atoms (of a certain isotope) to decay. This is called the isotopes Half-Life. For instance, it takes about 5730 years for half of a samples radioactive Carbon-14 atoms to decay, no matter the sample size. To this day, it is still unknown why this happens so certainly, but it definitely happens. We also cant determine which atom will decay at what time! Learn About It! Radioactive Decay Series Before we move past the atomic scale, there is one more important note on radiation. In some cases, decay is not one and done. After one decay, the isotope may still be unstable or excited, so another decay is needed to stabilize the isotope. This was touched upon with gamma decay. Large, very unstable isotopes may take quite a few steps to stabilize, especially in larger- mass isotopes (Uranium-238 is a good example). This multi-step process of nuclear reactions ending with a stable isotope is called a Radioactive Decay Series. Radiation On The Macroscopic Scale So, now we know the whys and hows about radiation on the atomic scale, but what about on our naked-eye, macroscopic scale? Can we measure it? Is it even important for anything? The answer is yes; radiation does not go unnoticed! Even though we cant directly see it, we can definitely observe its effects. We can measure it for safety precautions, scientific discoveries, and energy source research. One big difference from theoretical material weve covered so far is that we hardly ever see just one or a few radioactive atoms when we study their effects were more interested in tons and tons of radioactive atoms! But how will this change our view of decay for large samples and what we look for in nuclear reactions? Energy of Radiation Another macroscopic property of radiation we can measure is how the energy of radioactive decay effects the distance the radiation can travel, as well as how far it can pass through given materials! For instance, weve found that an alpha particle only travels a short distance and doesnt penetrate very far through materials when emitted. This is attributed to its high mass and slow speed in comparison to other types of decay, and thus, lower energy. Gamma rays, on the other hand, travel very fast over far distances, permeating far through many materials, due to their high-energy characteristic. Beta particles beat alphas in distance, speed, penetrating ability, and energy, but gamma rays take the cake! Background Radiation There are two main reasons why the speed, distance, and penetration matter to us in the macroscopic world! 1. Radiation is all around us in small, harmless doses. This naturally- occurring radiation is called background radiation. However, if we get careless, improper disposal of radioactive chemical waste can cause huge amounts of concentrated radioactivity, with doses hefty enough to do significant damage! 2. By evaluating the radiation around us, we can find out when we are at risk (higher energy, speed, etc. = more dangerous!). For instance, gamma rays can ionize tissue, easily damaging biological systems. The damages done by ionizing radiation can cause malfunctions in the process of cells! Ouch! Now, proceed to the next slide to Think About It! Think About It! Too Much Stuff! When the nucleus is packed with too many protons and neutrons, or when there are too many neutrons in comparison to the number of protons, the nucleus is unstable! One way to think of it is a person carrying too many books: With too many books, this guy cant keep them balanced! Hell have to lose a few books (undergo nuclear change) to regain his balance (return to a stable state)! Needs to lose stuff! Goes through Decay! Think About It! Can The Alchemists Dream Come True Back in the archaic times of chemistry, alchemists sought to turn Lead into Gold. Their methods only dealt with the bonding of elements, and thus, they never truly transmuted (changed from one element to another), but what about today? It is possible to force transmutations by firing high-energy neutrons through a particle accelerator at a sample of lead, causing it to change elements, but since this method is very costly and complex, the extremely small amount of gold formed would not be ready enough to turn a profit or compensate for the resources, as hoped by the alchemists. Think About It! Losing A Series Of Books If we think back to the guy holding tons of books, he would have to set some books down to keep his stack balanced. Most likely, setting just one book down isnt going to cut it. Large isotopes have the same problem! Theyll often decay multiple times (in a series) in order to stabilize. For instance, Uranium-238 has a radioactive decay series of 14 steps to reach a stable form, Lead! Think About It! Popcorn Popping! If you were making a bag of popcorn, would you be willing to bet your friend five bucks that you could guess which kernel would pop first? I wouldnt! Theres just way too many possibilities with no reasonable way of guessing! This is a great analogy for predicting the decay of atoms in a radioactive sample. So far, theres just no mathematical or statistical way to determine which exact atom will undergo a nuclear change at some given time, and good guessing wouldnt really help anyone! All we know is that the sample will lose half of its amount of radioisotope every half life. Thankfully, as of yet, we dont need to know which atom will decay at what time, nor the order of decay for the atoms. Until a brilliant nuclear chemist or nuclear physicist comes up with an application, the only thing wed get from it anyway would be bragging rights (or maybe five bucks)! Who knows, that nuclear scientist could be you! Think About It! Geiger Counters We discussed Background Radiation and the risks of high-dosage radiation, but how do we know where we are at risk? A Geiger Counter is an instrument that uses a low-pressure tube to sense, or count, interactions of ionizing radiation (a, B, and y, for example). These counts are indicated by audible clicks, produced when the radiation interacts with the gas in the tube and briefly conducts an electrical charge. More clicks means more radiation, and more radiation means the area youre inspecting is more dangerous! THINK YOU HAVE THE CONCEPTS DOWN? TEST YOUR KNOWLEDGE AND PROVE YOURSELF! SHOW THAT YOU ARE A MASTER OF NUCLEAR CHEMISTRY QUIZ! START THE QUIZ! QUESTION #1 Uraniu-238 is an isotope of Uranium that has almost 3 times as many neutrons as protons in its nucleus. It is very massive in comparison to isotopes found earlier on the periodic table. Would Uranium-238 be a radioactive isotope of Uranium? YESNO CORRECT! Yes, Uranium-238 is a radioactive isotope! It will emit an a-particle to become Thorium-234. Keep it up! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Alpha Decay! When an isotope of an element has a very large mass number ( a lot of protons and neutrons), a lot of energy is pent up excessively in the nucleus. To release this energy, an Alpha Particle may be released: An alpha particle is composed of 2 protons and 2 neutrons ( a Helium nucleus). When a-decay occurs, the isotopes element changes, becoming the element two places before it on the periodic table. Some examples can be seen on the next slide! LEARN ABOUT IT! ALPHA DECAY QUESTION #2 Name the three common types of radioactive decay discussed! a.) Alpha, Beta, Lambda b.) Omega, Mu, Gamma c.) Helium, Electron, Light d.) Alpha, Beta, Gamma CORRECT! Right! The three most common types of decay for Nuclear Chemistry are Alpha (a), Beta (B), and Gamma (y) Decay! Good work! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Types of Decay! LEARN ABOUT IT! TYPES OF RADIOACTIVITY Radiation is also referred to as radioactive decay. In the process of radioactive decay, the radioisotope throws stuff away from the nucleus. After all, the stuff in the nucleus is whats causing the problem, right? There are three main types of radioactive decay: Alpha Decay An alpha particle (a) is emitted from the unstable nucleus. An alpha particle essentially a helium nucleus (two neutrons, two protons) thrown from the radionuclide. Beta Decay A beta particle (B) is emitted from the unstable nucleus. A beta particle is essentially a high-energy electron (e-) thrown from the radionuclide. Gamma Decay Gamma radiation (y) is emitted from the unstable nucleus. A gamma ray is essentially very high-energy light thrown from the radionuclide. QUESTION #3 A nuclear change occurs in the nucleus of a radioisotope, and as a result, a high-energy electron is emitted. Name the type of decay that occurred! a.) Alpha b.) Beta c.) Gamma CORRECT! The emission of a high-energy electron due to a nuclear change is characteristic of beta decay, where the high-energy electron is also called a beta particle Way to go! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Beta Decay! LEARN ABOUT IT! BETA DECAY Early on in the periodic table, it is normal to see a stable isotope which has a proton-neutron ratio of about 1:1 (one proton for every neutron). However, as the number of protons in an atom gets very large down the periodic table, we see that isotopes are more stable when there are more neutrons than protons. Despite this, it is very possible for there to be too many neutrons, even considering the increased ratio. In this case, a neutron converts to a proton and an electron, where the proton stays bound in the nucleus, and the electron is emitted as a Beta Particle: The resulting proton changes the element and helps to balance the proton- neutron ratio. Thus, the Atomic Number increases by one, and Mass Number stays the same. QUESTION #4 A radioisotope of Carbon known as Carbon-14 has just undergone (B) decay and it is still quite unstable. If the atom then undergoes gamma decay to stabilize, what is the final product? CORRECT! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Examples of Beta Decay and Gamma Decay! LEARN ABOUT IT! EXAMPLES OF BETA DECAY LEARN ABOUT IT! GAMMA DECAY Alpha and beta decay both restore stability in the nucleus of an isotope by altering the number of protons and neutrons, but after these two types of decay, the atom is often left in an excited, energetic, unstable stable state. To further stabilize, the nucleus emits energy in the form of high-energy Gamma Rays: A gamma ray is an electromagnetic wave of very high frequency essentially, very high-energy invisible light. QUESTION #5 An ancient artifact is found containing a radioactive isotope throughout the sample! If the half-life of this isotope is 200 years, and 12.5% of the original amount of the isotope remains, how old is the artifact? Hint: How many half-lives have passed? a.) 400 years old c.) 600 years old b.) 200 years old d.) 1000 years old1000 CORRECT! Indeed! When 12.5% of the original isotope remains. 3 half-lives have passed, and for each half-life, 200 years have passed. So, 3 half-lives multiplied by 200 years equals 600 years passed! Excellent! 100% No Half-Lives 50% 1 Half-Life 200 years passed 25% 2 Half-Lives 400 years passed 12.5% 3 Half-Lives 600 years passed Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Half-Life of Isotopes! One nifty rule that we have figured out about radioactive samples on a macroscopic scale is that it takes a specific amount of time for half of the samples radioactive atoms (of a certain isotope) to decay. This is called the isotopes Half-Life. For instance, it takes about 5730 years for half of a samples radioactive Carbon-14 atoms to decay, no matter the sample size. To this day, it is still unknown why this happens so certainly, but it definitely happens. We also cant determine which atom will decay at what time! LEARN ABOUT IT! HALF-LIFE OF ISOTOPES QUESTION #6 How can we tell which atom is going to decay at a given time in a radioactive sample? a.) Measure other samples rate of radiation and calculate a pattern of decay b.) Collect data through one half-life, then use spatial analysis to find the atom c.) We cant its impossible so far CORRECT! Inconceivable! We cant do it as of yet. Scientists are stumped on how to predict which atom of a radioactive sample will decay next, or even when! If you checked out the Think It About! Section, you may recognize this by the Popping Popcorn sample! All we know is that there will be half of the original amount of isotope remaining once the time for a half-life has passed. However, knowing which atom will decay doesnt seem to have any benefits or advantages that would help as in any way, so for now, we are content with letting laws of nature handling this one. But who knows! It may become very important someday! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Popcorn Popping! If you were making a bag of popcorn, would you be willing to bet your friend five bucks that you could guess which kernel would pop first? I wouldnt! Theres just way too many possibilities with no reasonable way of guessing! This is a great analogy for predicting the decay of atoms in a radioactive sample. So far, theres just no mathematical or statistical way to determine which exact atom will undergo a nuclear change at some given time, and good guessing wouldnt really help anyone! All we know is that the sample will lose half of its amount of radioisotope every half life. Thankfully, as of yet, we dont need to know which atom will decay at what time, nor the order of decay for the atoms. Until a brilliant nuclear chemist or nuclear physicist comes up with an application, the only thing wed get from it anyway would be bragging rights (or maybe five bucks)! Who knows, that nuclear scientist could be you! THINK ABOUT IT! POPCORN POPPING! QUESTION #7 Considering the steps of radioactive decay, which statement is correct? a.) Often times, the decay of smaller-mass isotopes tends to be only one or two steps, whereas larger-mass isotopes tend to take many steps b.) Isotopes only decay once to stabilize, since the different types of decay can fit to any situation c.) Gamma decay can stabilize any isotope without needing to change the proton-neutron ratio, as long as it is allowed to go through several steps. CORRECT! Right! For smaller-mass isotopes, like Carbon-14, only one or two steps will take the radioisotope to a stable state, but for larger- mass isotopes, like Uranium-238, many steps may need to be taken to decay. This is not a set-in-stone rule, as the proton-neutron ratio may not be far off from stability when radioactive decay strikes. For instance, Cesium-137 may only take one or two steps to reach stability, despite its high mass in comparison to smaller radioisotopes. However, it is a good guideline to follow to predict general outcomes. An example of where this works comes back to Uranium-238, which may go through 14 steps of radioactive decay before it finally stabilizes and chills out. Great Choice! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Radioactive Decay Series! LEARN ABOUT IT! RADIOACTIVE DECAY SERIES Before we move past the atomic scale, there is one more important note on radiation. In some cases, decay is not one and done. After one decay, the isotope may still be unstable or excited, so another decay is needed to stabilize the isotope. This was touched upon with gamma decay. Large, very unstable isotopes may take quite a few steps to stabilize, especially in larger-mass isotopes (Uranium-238 is a good example). This multi-step process of nuclear reactions ending with a stable isotope is called a Radioactive Decay Series. If we think back to the guy holding tons of books, he would have to set some books down to keep his stack balanced. Most likely, setting just one book down isnt going to cut it. Large isotopes have the same problem! Theyll often decay multiple times (in a series) in order to stabilize. For instance, Uranium-238 has a radioactive decay series of 14 steps to reach a stable form, Lead! THINK ABOUT IT! LOSING A SERIES OF BOOKS QUESTION #8 Rank the types of decay in increasing order of the relative distance they can travel! Hint: shortest travel distance < middle travel distance < longest travel distance CORRECT! < < is right on the mark! Alpha particles travel the least distance (and also at the lowest speed), as they have such a large mass in comparison. Low mass beta particle, A.K.A high- energy electrons, travel further than alpha particles, not to mention much faster. However, a gamma ray beats them both by a long shot! This makes gamma radiation the most dangerous of the three because it can easily penetrate through a persons body! Nice Job Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Energy of Radiation! Another macroscopic property of radiation we can measure is how the energy of radioactive decay effects the distance the radiation can travel, as well as how far it can pass through given materials! For instance, weve found that an alpha particle only travels a short distance and doesnt penetrate very far through materials when emitted. This is attributed to its high mass and slow speed in comparison to other types of decay, and thus, lower energy. Gamma rays, on the other hand, travel very fast over far distances, permeating far through many materials, due to their high-energy characteristic. Beta particles beat alphas in distance, speed, penetrating ability, and energy, but gamma rays take the cake! LEARN ABOUT IT! ENERGY OF RADIATION QUESTION #9 Since natural background radiation can be found in small doses all around us, our bodies have grown accustomed to radiation, and thus, radiation in any amount wont damage our bodies. True or False? TRUEFALSE CORRECT! Although background radiation is often harmless, great concentrations of radiation can be very harmful, even fatal. Our bodies cant develop an immunity to radiation and cant really do much to fight it. That is why special suits and gear are worn while dealing with heavy radiation to protect the body, especially from gamma rays! Radical! Next Question! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Background Radiation! There are two main reasons why the speed, distance, and penetration matter to us in the macroscopic world! 1.Radiation is all around us in small, harmless doses. This naturally- occurring radiation is called background radiation. However, if we get careless, improper disposal of radioactive chemical waste can cause huge amounts of concentrated radioactivity, with doses hefty enough to do significant damage! 2.By evaluating the radiation around us, we can find out when we are at risk (higher energy, speed, etc. = more dangerous!). For instance, gamma rays can ionize tissue, easily damaging biological systems. The damages done by ionizing radiation can cause malfunctions in the process of cells! Ouch! LEARN ABOUT IT! BACKGROUND RADIATION Now, proceed to the next slide to Think About It! QUESTION #10 How can radiation damage organic matter (cells and tissues in living things)? a.) Radiation ionizes cells & tissues, breaking them down and causing malfunctions in their usual processes. b.) Radiation spa cells energy and shuts them down, since they cannot function without that vital cell energy c.) Biological tissues get energy from the mitochondria in cells, but the radiation forces extra energy into cells, exhausting them and burning them out CORRECT! Radiation bombards tissue, ionizing it and causing it to break apart. Biological tissues and cells are very complicated, and they are organized in a very specific way on the molecular level! When they are damaged and important parts of the organic machines are broken, malfunctions occur! And even worse, if the damaged cells multiply, duplicates of the damaged cells, continue to malfunction (cause of cancer)! Done with the Quiz! WHOOPS, TRY AGAIN! If you need help, check this out to review before you try again! Back to Background Radiation! There are two main reasons why the speed, distance, and penetration matter to us in the macroscopic world! 1.Radiation is all around us in small, harmless doses. This naturally- occurring radiation is called background radiation. However, if we get careless, improper disposal of radioactive chemical waste can cause huge amounts of concentrated radioactivity, with doses hefty enough to do significant damage! 2.By evaluating the radiation around us, we can find out when we are at risk (higher energy, speed, etc. = more dangerous!). For instance, gamma rays can ionize tissue, easily damaging biological systems. The damages done by ionizing radiation can cause malfunctions in the process of cells! Ouch! LEARN ABOUT IT! BACKGROUND RADIATION Now, proceed to the next slide to Think About It! CONGRATULATIONS! Excellent job on the quiz! Youve proven your expertise on the fundamentals of Nuclear Chemistry! Raise your hand and have Mr. Villegas check your screen, and hell write down your participation points for you! If you liked learning Nuclear Chemistry, youre in luck! This is only the beginning, and there is much more to explore! If youd like to know more about Nuclear Chemistry, there are plenty of websites and books that dive deeper into the world of atomic nuclei, and Mr. Villegas can give you suggestions on where to look! Also, click the link to check out the job description of a Nuclear Chemist! Sources Chemistry: The Central Science 10 th Edition, 2006 written information Office.com All Clipart https://www.youtube.com/watch?v=B8MOt6iVk7s review on reactions video https://www.youtube.com/watch?v=B8MOt6iVk7s- Decay Series Picture - CERN Particle Accelerator Picture er_Counter_(PFS).png Geiger Counter Pictureer_Counter_(PFS).png