CHAPTER 25 – NUCLEAR CHEMISTRY
Nuclear Radiation Standard -11c - many naturally occurring isotopes of elements are radioactive, as are isotopes formed in nuclear reactions. Standard -11d - the three most common forms of radioactive decay (alpha, beta, gamma) and how the nucleus changes in each type of decay. Standard - 11e - alpha, beta, and gamma radiation produce different amounts and kinds of damage in matter and have different penetrations
Vocabulary ________________________-the process by which nuclei emit particles and rays ________________________-the penetrating rays and particles emitted by a radioactive source ________________________-an isotope that has an unstable nucleus and undergoes radioactive decay. Radioactivity A. Radioactive Decay 1. Too many or too few neutrons relative to the number of protons makes a nucleus unstable. 2. An __________nucleus releases ________by emitting radiation during the process of radioactive ______. 3. _________radioisotopes of one element are transformed into_________ (nonradioactive) isotopes of a different element. 4. The spontaneous disintegration of a nucleus into a slightly lighter and more stable nucleus, accompanied by emission of particles, electromagnetic radiation, or both B. Nuclear Radiation 1. Particles or electromagnetic radiation emitted from the nucleus during ______________ C. Unstable Nuclides 1. All nuclides beyond atomic _________are unstable and radioactive III. Types of Radioactive Decay A. ___________________ 1. Alpha particle (α) is a _____________( 42 He), so it has a 2+ charge. 2. Alpha emission is restricted almost entirely to very heavy nuclei 210 206 4 84Po + → 82Pb+ 2 He 3. It is the most easily stopped of the three particles (____________________). It is the least dangerous. 4. Examples - Alpha radiation is emitted from U-238 238 234 4 92U → 90Th + 2He Alpha radiation is emitted from Rn-222____________________________ B. _______________________ 1. Beta particle (β) is an _____________from the nucleus during nuclear decay
2. Beta particles are emitted when a neutron is converted into a _______and an ________________ 3. It can be stopped by a ____________________or thin pieces of wood. 4. Example - ____________________________________ C. ___________________________ 1. Gamma rays (γ) are ________________________emitted from a nucleus as it changes from an excited state to a ground energy state 2. Gamma rays are produced when nuclear particles undergo transitions in energy levels 3. Gamma emission usually follows other types of decay (alpha and beta) that leave the nucleus in an excited state. 4. When the alpha particle is released a huge amount of energy is also released (the gamma particle)! 5. Example - 23090Th→22688Ra + 42He + γ 6. Gamma rays are the most penetrating. What will stop it?___________________ 25.2 Radioactive Decay I. Nuclear Stability and Decay A. ____________-an attractive force that acts between all nuclear particles that are extremely close together, like protons and neutrons in a nucleus B. _______________Ratio determines the type of decay that occurs 1. Band of Stability
C. Some nuclei have _______neutrons relative to the number of protons. These nuclei decay by turning a ________into a _______ to emit a ___________(an electron) from the nucleus. Beta emission 25.3 Fission and Fusion of Atomic Nuclei Standard - Describe what happens in a nuclear chain reaction. Explain the role of water in the storage of spent fuel rods. Distinguish fission reactions from fusion reactions. Nuclear Fission
A. Nuclear Fission 1. A very heavy nucleus ________into more ________ nuclei of intermediate mass 2. The mass of the products is less than the mass of the reactants. Missing mass is converted to energy a. Small amounts of missing mass are converted to _________________(E = mc2) 3. Occurs when nuclei of certain isotopes are bombarded with _________ 4. Example: ________________ 235 and _____________239 are the only fissionable isotopes. B. Nuclear Chain Reaction 1. A reaction in which the material that starts the reaction is also one of the products and can start another reaction 2. ________is used to moderate (slow down) neutrons in a nuclear reactor 3. Controlled nuclear chain reactions take place in ________________.
Nuclear Fusion A. Nuclear Fusion 1. Light-mass nuclei combine to form a heavier, more stable nucleus B. Fusion Reactions 1. More __________than fission reactions 2. Source of energy of the hydrogen bomb 3. Could produce energy for human use if a way can be found to contain a fusion reaction. Fusion reactions occur only at________________—in excess of 40,000,000°C. 25.4 Radiation in Your Life A. Penetrating Ability 1. _______________ a. Least penetrating ability due to large mass and charge b. Travel only a few centimeters through air c. Cannot penetrate skin d. Can cause harm through ingestion or inhalation 2. _______________ a. Travel at speeds close to the speed of light
b. Penetrating ability about 100 times greater than that of alpha particles. c. They have a range of a few meters in air. 3. ______________ a. Greatest penetrating ability b. Protection requires shielding with thick layers of lead, cement, or both