Introductory Chemistry (5th Edition)

Published by Pearson
ISBN 10: 032191029X
ISBN 13: 978-0-32191-029-5

Chapter 17 - Radioactivity and Nuclear Chemistry - Exercises - Problems - Page 638: 68

Answer

Partial decay series for Rn-220 is as follows:

Work Step by Step

Firstly, Rn-220 (Atomic number 86) undergoes alpha emission and as a result atomic number will be decreased by 2 and mass number will be decreased by 4 units. So, the new element has the atomic number 86-2 = 84 and mass number 220-4= 216. The new element is Po-216 (atomic number 84). When writing the nuclear equation, every element including alpha particle can be written in symbolic form (write the symbol of the element, write atomic number on the left subscript and write mass number on the left superscript of the symbol). Alpha particle is denoted by writing 'He' atom in symbolic form. Parent nuclide (Rn) is on the left side of the equation whereas daughter nuclide (Po) and alpha particle (He) will be on the right side of the equation. After that, for 2nd equation Po will become the parent nuclide. An alpha emission is occurred and the atomic number of new element will be 84-2 = 82 and mass number will be 216-4= 212. The new element will be Pb (atomic number 82). All elements including alpha particle will be represented in the symbolic form while writing the equation. For 3rd equation, Pb-212 (atomic number 82) will be the parent nuclide and it undergoes beta decay. The new element will have atomic number 82+1 = 83 and mass number will remain same (212). Now, we can represent parent element, new element and beta particle in symbolic form while writing the nuclear equation. Also, note that beta particle can be denoted as 'e' and left subscript is -1 while left superscript is 0. In the end, alpha emission occurs on Bi-83 and the new element will have atomic number 83-2 = 82; mass number = 212-4= 208. Every element including alpha particle is represented in symbolic form when writing the nuclear equation. For every equation, Parent nuclide will be on the left side of the equation whereas daughter nuclide and the emitted particle will be on the right side of the equation.
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