1. HOMEWORK # 5 Isotopes WS

2. Aim # 5: What are isotopes?

3. 3 REVIEW Using the periodic table, specify the atomic mass of each element (round to the tenths place): A.calcium B. aluminum C. lead D. barium E. iron

4. How do you find the mass number of Sodium ? Number of Neutrons = Mass Number- Atomic Number 23 Na - 11 12

5. Why are decimals in the atomic mass?

7. Isotopes and Mass Number ElementMass Number Atomic Number Number of Neutrons % Abundance Protium11099.985 Deuterium2110.0151 Tritium312trace

8. ElementMass Number Atomic Number Number of Neutrons % Abundance Carbon-12126698.9 Carbon-141468trace

9. 16 8 O 17 8 O 18 8 O ElementMass Number Atomic Number Number of Neutrons % Abundanc e Oxygen-16168899.76 Oxygen-1717890.03 Oxygen-18188100.20

10. 53 I

11. How do we deal with the fact that some atoms have several isotopes? The solution is to measure the mass of each individual isotope in the element and then calculate the weighted average. The weighted average is known as the atomic mass of the element

12. 1. Atomic Mass Measured using the mass spectrometer The neutral atom of the isotope of carbon-12 is the appropriate standard Carbon-12 has a mass of 12 atomic mass units (12 amu) One atomic mass unit is 1/12 of the mass of a carbon-12 atom

13. 2. Isotopes Isotopes are atoms with the same atomic number (number of protons) but a different number of neutrons, and mass number Isotopes have the same chemical properties, but different physical properties (physical properties: boiling point, melting point, atomic mass, etc

14. 3. How do you write the name of an isotope? C-12 or Carbon -12 C-14 or carbon-14 Chemical symbol and the mass number of the element. Is there any other way to write an isotope? Yes. Nitrogen with 8 neutrons may be written Nitrogen-15.

15. 15 4. Calculating Atomic Mass Atomic mass = (mass isotope 1 ) (%) + (mass isotope 2 ) (%) + ………… 100 100

16. 16 Exercise # 1 Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium- 69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium? Gallium-6968.9 amu60.2% Gallium-7170.9 amu39.8%

17. 17 Solution Set up the problem: 68.9 amu x 60.2 + 70.9 amu x 39.8 100 100 Atomic mass Ga = 69.70 amu

18. 18 Exercise # 2 Isotopes Mass of Isotope Abundance 24 Mg 24.0 amu 78.70% 25 Mg 25.0 amu 10.13% 26 Mg 26.0 amu 11.17% Find the atomic mass off Mg atom

19. 24.0 amu x 78.70 + 25.0 amu x 10.13 + 26.0 amu x 11.17 100 100 100 = 24.3 amu

21. Base your answers to questions 54 through 57 on the information below. 54. State, in terms of subatomic particles, how an atom of Cu-63 differs from an atom of Cu-65. [1]

22. Base your answers to questions 54 through 57 on the information below. 55. What is the total number of electrons in an atom of Cu-65? [1] 56. The atomic mass of Cu-63 is expressed to what number of significant figures? [1]

23. 57. In the space in your answer booklet, show a correct numerical setup for calculating the atomic mass of copper. [1]

24. August 2007 54 Determine the total number of neutrons in an atom of Si-29. [1] 55 In the space in your answer booklet, show a correct numerical setup for calculating the atomic mass of Si. [1]

25. 56 A scientist calculated the percent natural abundance of Si-30 in a sample to be 3.29%. Determine the percent error for this value. [ 1 ]

26. 26 QUESTION #1 Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12 C 13 C 14 C 6 6 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______

27. 27 Solution Q1 12 C 13 C 14 C 6 6 6 #P __6___ _ 6___ ___6___ #N __6___ _ _7___ ___8___ #E __6___ _ 6___ ___6___

28. 28 QUESTION 2 An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 302) 353) 65 B.Number of neutrons in the zinc atom 1) 302) 353) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 372) 653) 67

29. 29 SOLUTION Q2 An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 30 B.Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67

30. 30 Question #3 Write the atomic symbols for atoms with the following: A. 8 p +, 8 n, 8 e - ___________ B.17p +, 20n, 17e - ___________ C. 47p +, 60 n, 47 e - ___________

31. 31 Solution Q 3 16 O A. 8 p +, 8 n, 8 e - 8 B.17p +, 20n, 17e - 37 Cl 17 C. 47p +, 60 n, 47 e - 107 Ag 47

32. 32 Question # 4 An atom has 14 protons and 20 neutrons. A.Its atomic number is 1) 142) 163) 34 B. Its mass number is 1) 142) 163) 34 C. The element is 1) Si2) Ca3) Se D.Another isotope of this element is 1) 34 X 2) 34 X 3) 36 X 16 14 14

33. 33 Solution Q 4 An atom has 14 protons and 20 neutrons. A.It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si D.Another isotope of this element would be 3) 36 X 14