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# Atoms and elements by deepika

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### Atoms and elements by deepika

1. 1. Atoms and ElementsIsotopes and Atomic Mass 24Mg 25Mg 26Mg 12 12 12 1
2. 2. IsotopesIsotopes Are atoms of the same element that have different mass numbers. Have the same number of protons, but different numbers of neutrons. 2
3. 3. Nuclear SymbolA nuclear symbol Represents a particular atom of an element. Gives the mass number in the upper left corner and the atomic number in the lower left corner. Example: An atom of sodium with atomic number 11 and a mass number 23 has the following atomic symbol: mass number 23 Na atomic number 11 3
4. 4. Nuclear SymbolsFor an atom, the nuclear symbol gives the number of Protons (p+) Neutrons (n) Electrons (e-) 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8n 16 n 35 n 8 e- 15 e- 30 e- 4
5. 5. Learning CheckNaturally occurring carbon consists of three isotopes,12C, 13C, and 14C. State the number of protons,neutrons, and electrons in each of the following. 12C 13C 14C 6 6 6protons ______ ______ ______neutrons ______ ______ ______electrons ______ ______ ______ 5
6. 6. Solution 12C 13C 14C 6 6 6protons 6 p+ 6 p+ 6 p+neutrons 6n 7n 8nelectrons 6 e- 6 e- 6 e- 6
7. 7. Learning CheckWrite the nuclear symbols for atoms with thefollowing subatomic particles:A. 8 p+, 8n, 8e- ___________B. 17p+, 20n, 17e- ___________C. 47p+, 60 n, 47 e- ___________ 7
8. 8. Solution 16OA. 8p+, 8n, 8e- 8B. 17p+, 20 n, 17e- 37Cl 17C. 47p+, 60n, 47e- 107Ag 47 8
9. 9. Learning Check1. Which of the following pairs are isotopes of the same element?2. In which of the following pairs do both atoms have 8 neutrons?A. 15X 15X 8 7B. 12X 14X 6 6C. 15X 16X 7 8 9
10. 10. SolutionB. 12X 14X 6 6 Both nuclear symbols represent isotopes of carbon with six protons each, but one has 6 neutrons and the other has 8.C. 15X 16X 7 8 An atom of nitrogen (7) and an atom of oxygen (8) each have 8 neutrons. 10
11. 11. Isotopes of MagnesiumIn naturally occurring magnesium,there are three isotopes. Isotopes of MgAtomic Mass 23.99 24.98 25.98% abundance 78.70 10.13 11.17Copyright © 2007 by Pearson Education, Inc. 24Mg 25Mg 26MgPublishing as Benjamin Cummings 12 12 12 11
12. 12. Isotopes of SulfurA sample of naturallyoccurring sulfur containsseveral isotopes with thefollowing abundancesIsotope % abundance32S 95.0233S 0.75 32S, 33S, 34S, 36S34S 16 16 16 16 4.2136S 0.02 12
13. 13. Atomic MassThe atomic mass of an element Is listed below the symbol of each Na element on the periodic table. 22.99 Gives the mass of an “average” atom of each element compared to 12C. Is not the same as the mass number. 13
14. 14. Some Elements and Their AtomicMassMost elements have two or more isotopes thatcontribute to the atomic mass of that element.TABLE 2.9 32.07 amu 14
15. 15. Atomic Mass for ClThe atomic mass of chlorine is Based on all naturally occurring Cl isotopes. Not a whole number. The weighted average of 35Cl and 37Cl. Copyright © 2007 by Pearson Education, Inc. 15 Publishing as Benjamin Cummings
16. 16. Learning CheckUsing the periodic table, give the atomic mass ofeach element:A. calcium __________B. aluminum __________C. lead __________D. barium __________E. iron __________ 16
17. 17. SolutionUsing the periodic table, give the atomic mass ofeach element:A. calcium 40.08 amuB. aluminum 26.98 amuC. lead 207.2 amuD. barium 137.3 amuE. iron 55.85 amu 17
18. 18. The EndThanking You 18