Friday, 05/06/16 1) Warm-up: If you start with 100g of a radioactive substance, how much will be left after 3 half-lives? 2) Review HW & Nuclear Notes 3) Complete Modeling Energy Investigation 4) Complete: Nuclear Half-Life Investigation- Link on Weekly Schedule 5) Nuclear reaction equation practice 6) HW QUIZ MONDAY Learning Target (NEW) I CAN: describe the role of neutrons in the nucleus and the importance of the band of stability & describe three different types of radiation: alpha, beta, and gamma.
14.4 Chemical vs. Nuclear Reactions The involvement of energy in chemical reactions has to do with the breaking and forming of chemical bonds. A nuclear reaction involves altering the number of protons and/or neutrons in an atom.
14.4 Radioactivity Almost all elements have one or more isotopes that are stable. Stable means the nucleus stays together. Carbon-14 is radioactive because it has an unstable nucleus.
14.4 Radioactive Decay This process of radioactive decay results in an unstable, radioactive isotope like carbon-14 becoming the more stable isotope nitrogen-14.
14.4 Radioactive Decay There are three types of radioactive decay: 1. alpha decay, 2. beta decay, and 3. gamma decay.
14.4 Two types of Nuclear Reactions There are two kinds of nuclear reactions: fusion and fission. Nuclear fusion is the process of combining the nuclei of lighter atoms to make heavier atoms.
14.4 Fusion Nuclear fusion occurs in the Sun and the resulting energy released provides Earth with heat and light.
14.4 Types of Nuclear Reactions Nuclear fission is the process of splitting the nucleus of an atom. A fission reaction can be started when a neutron bombards a nucleus.
14.4 Using nuclear reactions in medicine and science A half-life is a certain length of time after which half of the amount of radioactive element has decayed. As a radioactive element decays, it emits harmful radiation such as alpha and beta particles and gamma rays.
14.4 Using nuclear reactions Radioactive dating is a process used to figure out the age of objects by measuring the amount of radioactive material in it and by knowing the half-life of that substance. Understanding radioactive decay of uranium-238 has allowed scientists to determine that the age of Earth is 4.6 billion years old.
14.4 Using nuclear reactions in medicine and science Radioisotopes (also called radioactive isotopes) are commonly used as tracers in medicine and science. By adding a radioactive isotope into a system (such as the human body or an underground water supply), problems can be detected.
1. Why is so much energy required and released in a nuclear reaction? 2. Gold-185 decays to iridium- 181. Is this an example of alpha or beta decay? 3. What has to happen, in terms of radioactive decay, for carbon- 14 to decay to nitrogen-14? 4. How is gamma decay different from alpha or beta decay? 1. A great deal of energy is required for and released in nuclear reactions because these reactions involve separating the particles in the nucleus of an atom. These particles are held together by strong nuclear force, the strongest force known to science 2. The decay of gold-185 to iridium-181 is an example of alpha decay because the atomic mass decreases by four and the atomic number decreases by two (from 79 for gold to 77 for iridium). 3. Beta decay has to occur for carbon-14 (atomic number 6) to decay to nitrogen-14 (atomic number 7). In this case, a neutron is split into a proton and an electron, so the atomic number increases by one but the atomic mass stays the same. 4. Gamma decay involves only the release of energy from the nucleus whereas both alpha and beta decay involve the release of particles.
5. In your own words, describe the difference between fusion and fission. Why do certain elements undergo fusion or fission? 6. Which type of nuclear reaction is used in modern-day nuclear reactors? Why is the other type of nuclear reaction NOT used in modern-day energy production? 7. When an atom of beryllium-9 is bombarded by an alpha particle, an atom of carbon-12 is produced and a neutron is emitted. What kind of nuclear reaction has just occurred? 5. Fusion is a nuclear reaction that involves two nuclei fusing together and producing/ releasing energy and particles. Fission is a nuclear reaction that involves radioactive decay. Both fusion and fission result in one element transforming into a different element. Radioactive isotopes are the starting materials for nuclear reactions. Radioactive isotopes are unstable because their nuclei get too full of protons or neutrons to hold together by strong nuclear force. 6. Fission is used in modern day nuclear reactors. Fusion is not used because too much energy is required to initiate these types of reactions. 7. The transformation of beryllium-9 to carbon- 12 is a fusion reaction because the alpha particle (a helium nucleus) fused with the beryllium nucleus.
8. What is the half-life of each of these radioactive isotopes? a. A radioactive isotope decreased to one-half its original amount in 18 months. b. A radioactive isotope decreased to one-fourth its original amount in 100 years. 9. For each scenario below, indicate whether a chemical reaction or a nuclear reaction is occurring. a. When two compounds are combined, heat is released. b. A sample of galium-68 is reduced to one-half of its original amount in 68.3 minutes. c. Radium-226 decays to radon-222. d. A spark of energy is used to begin combustion of methane. e. Hydrogen nuclei fuse in the Sun to make helium atoms. 8. Answers: a. The half-life is 18 months. b. The half-life is 50 years. After 50 years the isotope was at one-half, then after another 50 years, the isotope was at one-fourth. 9. Answers: a. Chemical b. Nuclear c. Nuclear d. Chemical e. Nuclear