HOMEWORK # 5 Isotopes WS

Aim # 5: What are isotopes?

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

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

Why are decimals in the atomic mass?

Isotopes and Mass Number ElementMass Number Atomic Number Number of Neutrons % Abundance Protium Deuterium Tritium312trace

ElementMass Number Atomic Number Number of Neutrons % Abundance Carbon Carbon trace

16 8 O 17 8 O 18 8 O ElementMass Number Atomic Number Number of Neutrons % Abundanc e Oxygen Oxygen Oxygen

53 I

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

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

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

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

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 amu60.2% Gallium amu39.8%

17 Solution Set up the problem: 68.9 amu x amu x Atomic mass Ga = amu

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

24.0 amu x amu x amu x = 24.3 amu

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]

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]

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

August 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]

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 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 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______

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

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 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 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 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 Ag 47

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

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