Nuclear Chemistry Table of Contents Section 1 What Is Radioactivity? Section 2 Nuclear Fission and Fusion Section 3 Nuclear Radiation Today
Section 1 What Is Radioactivity? Bellringer Before studying about nuclear chemistry, answer the following items to refresh your memory about the structure of the nucleus. 1. Label the diagram shown below.
Section 1 What Is Radioactivity? Bellringer, continued 2. Complete the table to indicate how many protons and netrons are in the nuclei of the following atoms:
Section 1 What Is Radioactivity? Nuclear Radiation The process by which an unstable nucleus emits one or more particles or energy in the form of electromagnetic radiation is called radioactivity. The particles that are released from the nucleus during radioactive decay is called nuclear radiation. There are different types of nuclear radiation.
Section 1 What Is Radioactivity? Types of Nuclear Radiation
Section 1 What Is Radioactivity? Comparing Alpha, Beta, and Gamma Particles
Section 1 What Is Radioactivity? Nuclear Radiation, continued Alpha particles consist of protons and neutrons. An alpha particle is a positively charged atom that is released in the disintegration of radioactive elements and that consists of two protons and two neutrons. Beta particles are electrons produced from neutron decay. A beta particle is a charged electron emitted during certain types of radioactive decay, such as beta decay.
Section 1 What Is Radioactivity? Nuclear Radiation, continued Gamma rays are very high energy. A gamma ray is a high-energy photon emitted by a nucleus during fission and radioactive decay. Neutron radioactivity may occur in unstable nucleus. Neutron emission consists of matter that is emitted from an unstable nucleus. Neutrons are able to travel farther through matter than either alpha or beta particles.
Section 1 What Is Radioactivity? Nuclear Decay In nuclear decay, the sums of the mass numbers and the atomic numbers of the decay products equal the mass number and atomic number of the decaying nucleus. A nucleus gives up two protons and two neutrons during alpha decay. The process of the alpha decay of radium-226 is written as follows. 226 Ra 222 Rn 4 He 226 222 4 88 86 2 88 86 2
Section 1 What Is Radioactivity? Nuclear Decay, continued A nucleus gains a proton and loses a neutron during beta decay. A beta decay process occurs when carbon-14 decays to nitrogen-14 by emitting a beta particle. 14 C 14 N 0 e 14 14 0 6 7 Š1 6 7 (Š1)
Section 1 What Is Radioactivity? Alpha, Beta, and Gamma Radiation
Section 1 What Is Radioactivity? Math Skills Nuclear Decay Actinium-217 decays by releasing an alpha particle. Write the equation for this decay process, and determine what element is formed. 1. Write down the equation with the original element on the left side and the products on the right side. Use the letter X to denote the unknown product. Note that the mass and atomic numbers of the unknown isotope are represented by the letters A and Z. 217 C A X 89 Z 2 4 He
Section 1 What Is Radioactivity? Math Skills, continued 2. Write math equations for the atomic and mass numbers. 217 = A 4 89 = Z 2 3. Rearrange the equations. A = 217 4 Z = 89 2 4. Solve for the unknown values, and rewrite the equation with all nuclei represented. A = 213 Z = 87 The unknown decay product has an atomic number of 87, which is francium, according to the periodic table. The element is therefore 213 Fr. 217 C 213 Fr 4 He 87 89 87 2
Section 1 What Is Radioactivity? Radioactive Decay Rates The half-life is the time required for half of a sample of a radioactive substance to disintegrate by radioactive decay or by natural processes. Half-life is a measure of how quickly a substance decays. Using half-lives, scientist can predict how old an object is. Carbon-14 is used to date materials.
Section 1 What Is Radioactivity? Half-Life
Section 1 What Is Radioactivity? Half-Life
Section 1 What Is Radioactivity? Math Skills Half-life Radium-226 has a half-life of 1599 years. How long would it take seven-eighths of a radium-226 sample to decay? 1. List the given and unknown values. Given: half-life = 1599 years fraction of sample decayed = 7/8 Unknown: fraction of sample remaining =? total time of decay =?
Section 1 What Is Radioactivity? Math Skills, continued 2. Calculate the fraction of radioactive sample remaining. To find the fraction of sample remaining, subtract the fraction that has decayed from 1. fraction of sample remaining = 1 Š fraction decayed fraction of sample remaining = 1 7 1 8 8 3. Calculate the number of half-lives. Amount of sample remaining after one half-life = 1 2 Amount of sample remaining after two half-lives = 1 2 1 2 1 4
Section 1 What Is Radioactivity? Math Skills, continued 3. Calculate the number of half-lives (continued). Amount of sample remaining after three half-lives = 1 1 1 1 2 2 2 8 Three half-lives are needed for one-eighth of the sample to remain undecayed. 4. Calculate the total time required for the radioactive decay. Each half-life lasts 1599 years. 1599 y total time of decay = 3 half-lives half-life 4797 years
Section 2 Nuclear Fission and Fusion Nuclear Forces Nuclei are held together by a special force. Protons and neutrons are tightly packed in the tiny nucleus of an atom. The strong nuclear force causes protons and neutrons in the nucleus to attract each other. This attraction is much stronger than the electric repulsion between protons. Neutrons contribute to nuclear stability. Too many neutrons or protons can cause a nucleus to become unstable and decay.
Section 2 Nuclear Fission and Fusion Forces in the Nucleus
Section 2 Nuclear Fission and Fusion Nuclear Fission Fission is the process by which a nucleus splits into two or more fragments and releases neutrons and energy. One type of fission of uranium-235 can be represented by the following equation. 235 U 1 92 0 n 137 Ba 84 56 36 Kr 15 1 0 n energy
Section 2 Nuclear Fission and Fusion Nuclear Fission
Section 2 Nuclear Fission and Fusion Nuclear Fission, continued Energy is released during a nuclear fission. The equivalence of mass and energy observed in nature is explained by the special theory of relativity. This equivalence is expressed by the following equation. Mass-Energy Equation Energy mass speed of light 2 E mc 2
Section 2 Nuclear Fission and Fusion Nuclear Fission, continued Neutrons released by fission can start a chain reaction. A nuclear chain reaction is a continuous series of nuclear fission reactions. Chain reactions can be controlled. If there is less than a critical mass of a fissionable isotope, a chain reaction will not occur. The critical mass is the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction.
Section 2 Nuclear Fission and Fusion Chain Reaction
Section 2 Nuclear Fission and Fusion Nuclear Chain Reaction
Section 2 Nuclear Fission and Fusion Critical Mass
Section 2 Nuclear Fission and Fusion Nuclear Fusion Nuclear fusion is the process in which light nuclei combine at extremely high temperature, forming heavier nuclei and releasing energy. Nuclear fusion occurs in the sun. Four hydrogen atoms fuse together in a multi-step process to produce a helium atoms and enormous energy in the form of gamma rays. 1 H 1 1 1 H 2 H two particles 1 2 H 1 1 1 H 3 0 He 2 0 3 He 3 2 2 He 4 He 1 2 1 H 1 1 H
Section 2 Nuclear Fission and Fusion Nuclear Fusion
Section 3 Nuclear Radiation Today Where is Radiation? Nuclear radiation is all around you. Background radiation is the nuclear radiation that arises naturally from cosmic rays and from radioactive isotopes in the soil and air. Radiation is measured in units of rems. A rem is the quantity of ionizing radiation that does as much damage to human tissue as 1 roentgen of high-voltage X rays does.
Section 3 Nuclear Radiation Today Where is Radiation?, continued Exposure varies from one location to another. Some activities add to the amount of nuclear radiation exposure.
Section 3 Nuclear Radiation Today Beneficial Uses of Nuclear Radiation Smoke detectors help to save lives. In a smoke alarm, a small alpha-emitting isotope detects smoke particles in the air. Nuclear radiation is used to detect diseases. A radioactive tracer is a radioactive material that is added to a substance so that its distribution can be detected later. Radioactive tracers are widely used in medicine.
Section 3 Nuclear Radiation Today Radioactive Tracer
Section 3 Nuclear Radiation Today Beneficial Uses of Nuclear Radiation, continued Nuclear radiation therapy is used to treat cancer. Radiotherapy is treatment that uses controlled doses of nuclear radiation for treating diseases such as cancer. Agriculture uses radioactive tracers and radio-isotopes. On research farms, radioactive tracers help scientists to understand biochemical processes in plants.
Section 3 Nuclear Radiation Today MRI Image of a Healthy Brain
Section 3 Nuclear Radiation Today MRI Image of Brain with Alzheimer s
Section 3 Nuclear Radiation Today Possible Risks of Nuclear Radiation Nuclear radiation can ionize atoms. Ionization is a change in the number of electrons in an atom or molecule, causing the particle to be positively or negatively charged. Radiation sickness results from high levels of nuclear radiation. People working in radioactive areas wear a dosimeter, a device that measures the amount of nuclear radiation exposure. Studies have shown a relationship between exposure to high levels of nuclear radiation and cancer.
Section 3 Nuclear Radiation Today Possible Risks of Nuclear Radiation The risk depends upon the amount of radiation exposure. High concentrations of radon gas can be hazardous. Radon gas is colorless and odorless, and is produced by the decay of uranium-238 present naturally in soil and rock. Tests for radon gas are widely available
Section 3 Nuclear Radiation Today Nuclear Power Nuclear fission has both advantages and disadvantages. Nuclear fission is an alternative to fossil fuels as a source of energy. Radioactive products of fission must be handled carefully and nuclear waste must be safely stored. Nuclear fusion reactors are being tested. Nuclear fusion reactions are difficult to produce in the laboratory. Nuclear fusion also has advantages and disadvantages.
Section 3 Nuclear Radiation Today Nuclear Energy