CM-UY 1004 Lecture Notes - Lecture 1: Half-Life, Intensive And Extensive Properties

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limehamster162

2 Sep 2016

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Since mass and charge must be balanced on both sides, you can use this concept to find missing reactants and missing products. Natural transmutation: the previously described transmutations that occur as a result of unstable proton to neutron ratios. Artificial transmutation always has two reactants while natural only has one. Technically in nuclear reactions there is a small difference of mass in the reactants and products, The loss of mass in nuclear reactions is due to a conversion of mass to energy (e = mc2) Mass defect: the matter than has been converted into energy. Nuclear reactions release way more energy than regular, and the more mass lost the more energy released. When a heavy nucleus is bombarded with a neutron and it splits into two middle weight nuclei and some neutrons. When two light nuclei combine to form heavier ones (like with hydrogen) Fusion releases a ton of energy (more than fission)

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Nuclear Decay Equations

Learning Goal:

To predict the products of alpha emission, beta emission, positron emission, and electron capture.

Radioactivity is the spontaneous emission of radiation from an unstable nucleus. There are five major types of radioactive decay:

Alpha (Î±) radiation consists of helium nuclei. The helium nucleus is a small particle containing two protons and two neutrons (42He).

Beta (Î²) radiation consists of electrons. In nuclear equations, the standard format for representing a beta particle using superscripts and subscripts is 0â1e.

Positron emission results from the conversion of a proton in the nucleus to a neutron. The ejected positron is a particle that has the same mass as an electron but an opposite charge. In nuclear equations, the standard format for representing a positron using superscripts and subscripts is 01e .

Electron capture is the capture of an inner shell electron by a proton in the nucleus. The process emits gamma (Î³) radiation and results in a proton converting to a neutron. Gamma radiation consists of high-energy electromagnetic radiation.

Gamma (Î³) radiation consists of high-energy radiation, and contains no particles and thus they have no mass. In nuclear equations, the standard format for representing gamma radiation using superscripts and subscripts is 00Î³.

Balancing a decay equation

There are two main rules to remember when balancing nuclear equations:

The total of the superscripts in the reactants and products must be the same.

The total of the subscripts in the reactants and products must be the same.

For an isotope of an element, the superscripts are mass numbers, and the subcripts are atomic numbers:

Mass number â¶ AAtomic number â¶ Z X âµ Chemical symbol

Where the mass number (A) is the sum of the number of proton and number of neutrons in the nucleus, atomic number (Z) is the number of protons in the nucleus, and chemical symbol (X) is the symbol of the specific element.

Part A

Identify the nuclide produced when americium-241 decays by alpha emission:

241 95Amâ42He + ?

Express your answer as an isotope using prescripts.

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Part B

Identify the nuclide produced when phosphorus-32 decays by beta emission:

3215Pâ 0â1e + ?

Express your answer as an isotope using prescripts.

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Part C

Identify the nuclide produced when fluorine-18 decays by positron emission:

18 9Fâ01e + ?

Express your answer as an isotope using prescripts.

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Part D

Identify the nuclide produced when thallium-201 decays by electron capture:

201 81Tl+ 0â1eâ00Î³ + ?

Express your answer as an isotope using prescripts.

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(a) Which of the following statements about the uranium used in nuclear reactors is or are true? (i) Natural uranium has too little ²³⁵U to be used as a fuel. (ii) ²³⁸U cannot be used as a fuel because it forms a supercritical mass too easily. (iii) To be used as fuel, uranium must be enriched so that it is more than 50% ²³⁵U in composition. (iv) The neutron-induced fission of ²³⁵U releases more neutrons per nucleus than fission of ²³⁸U. (b) Which of the following statements about the plutonium shown in the chapter-opening photograph explains why it cannot be used for nuclear power plants or nuclear weapons? (i) None of the isotopes of Pu possess the characteristics needed to support nuclear fission chain reactions. (ii) The orange glow indicates that the only radioactive decay products are heat and visible light. (iii) The particular isotope of plutonium used for RTGs is incapable of sustaining a chain reaction. (iv) Plutonium can be used as a fuel, but only after it decays to uranium.

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1. (1 point) What might be damaged by ionizing radiation? * paper soft tissue wood lead

2. (1 point) When an atom emits an beta particle, what is the change in the atomic number? * no change decrease by 1 decrease by 2 increase by 1 increase by 2

3. (1 point) What is the change in atomic mass caused by the emission of gamma radiation? * no change decrease by 1 decrease by 2 increase by 1 increase by 2

4. (1 point) Which of the following materials would effectively stop gamma radiation? * one foot of concrete single sheet of paper thin pieces of wood three inches of lead

5. (1 point) When the ratio of neutron-to-proton dictates that a neutron must break down it will form _________. * A helium nucleus An alpha particle A proton and an electron Two protons

6. (1 point) What determines the type of decay if a nucleus falls outside the band of stability? * the ratio of alpha particles to beta particles the ratio of beta particles to alpha particles the ratio of neutrons to protons the ratio of protons to neutrons

7. (1 point) A positron is emitted when ____________. * an alpha particle forms a beta particle forms proton converts to a neutron neutron converts to a proton

8. (1 point) How does an atom with too few neutrons relative to protons undergo radioactive decay? * by converting proton to a neutron by converting a neutron to a proton by emitting an alpha particle by emitting a beta particle

9. (1 point) How much of the original sample would remain after two half lives have past? * There would be nothing of the original left There would be half of the original sample still there There would be one quarter of the sample still present There would only be one eighth of the original sample still present

10. (1 point) What is the approximate half life of carbon- 14? * hundreds of years thousands of years million of years billion of years

11. (1 point) A reaction where a heavier nucleus splits into smaller nuclei is called ___________. * a chemical reaction background radiation fission fusion

12. (1 point) __________ and ___________ are used as moderators to capture neutrons in a nuclear reactor. * Cadmium and other metal Carbon and water Liquid sodium and water Plutonium and neptunium

13. (1 point) For a person working in a place where they might be exposed to radiation a _________ is routinely used to check their exposure. * film badge Geiger counter moderating rod scintillation counter

14. (1 point) Radioisotopes are used to do all of the following except __________. * analyze matter. diagnose medical problems. improve the flavor of food. treat diseases. study plant growth. Open response questions: Answer the following with complete sentences or if math is involve show the work

15. (3 point) The radioisotope radon-222 has a half-life of 3.8 days. How much of a 198.6 g sample of radon -222 would be left after approximately 23 days? ( Show your work) * Your answer

16. (3 point) How can an element be artificially transmuted? Give an example that has an element and what it is transmuted into. * Your answer

17. (4 point) Why does the mass and charge of an alpha particle make it less penetrating than a beta or gamma? Discuss both the mass and the charge(2 points each). *

CM-UY 1004 Lecture Notes - Lecture 1: Half-Life, Intensive And Extensive Properties

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