CHEM 1070 Chapter Notes - Chapter 17: Nuclide, Alpha Particle, Nucleon

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30 Nov 2016

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Radioactivity: the emission of tiny, invisible, energetic particles from the unstable nuclei of atoms, many of these particles can penetrate matter. Radioactive: describes a substance that emits tiny, invisible, energetic particles from the nuclei of its component atoms. Phosphorescence: the slow, long-lived emission of light that sometimes follows the absorption of light by some atoms and molecules. Alpha radiation: radiation emitted by an unstable nucleus, consisting of alpha particles. Alpha particle: a particle consisting of two protons and two neutrons. High ionizing power and low penetrating power. Nuclear equation: an equation that represents the changes that occur during radioactivity and other nuclear processes. Parent nuclide: the original nuclide in a nuclear decay. Daughter nuclide: the nuclide product of a nuclear decay. Ionizing power: the ability of radiation to ionize other molecules and atoms. Penetrating power: the ability of a radioactive particle to penetrate matter. Beta radiation: energetic electrons emitted by an unstable nucleus.

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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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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). *

Neutron activation has an important application in analyzing the trace elements from a sample. It can also be employed in the treatment of brain tumors where is consumed in the form of medicine or intravenous injection. This isotope is attracted by tumor cells and activated by neutrons. The isotope captures the neutrons (1 n 0), forming radioactive boron, which disintegrates into lithium and alpha particles ( 4 a 2 or 4 He 2 ). This disintegration produces energy in the form of gamma radiations (y) that kills the tumor cells in the vicinity of boron nuclei. This form of cancer treatment is known as boron neutron capture therapy (BNCT).Part BBNCT relies on the initial targeting of tumor cells by an appropriate chemical compound tagged with 10 B 5, which preferentially concentrates in tumor cells. During the irradiation of the tumor site by neutrons (1 n 0) the 10 B 5 absorbs a low-energy neutron (1 n 0), and it ejects an energetic short-range alpha particle ( 4 a 2 or 4 He 2 ) and lithium ion along with gamma radiation (y). This radiation deposits most of its energy within the cell containing the original 10 B 5 atom. Therefore, if a higher concentration of 10 B 5 exists in tumor cells relative to other normal tissues, a concomitantly higher dose will be delivered to the tumor cells during neutron irradiation.What is the nuclear reaction that takes place in the tumor cell?

CHEM 1070 Chapter Notes - Chapter 17: Nuclide, Alpha Particle, Nucleon

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