1. Average Atomic Mass

2. Drill
Take a few minutes to look over your notes for your quiz!! 

3. Agenda
Quiz
Average Atomic Mass Notes and Practice
Candium Lab HW

4. I Can…
Calculate the average atomic mass for an element

5. Average Atomic Mass
The weighted average mass of all the isotopes found in nature for that element

6. Units
Average Atomic Mass is measured in atomic mass units (amu)

7. Mass Spectrometer
Instrument that determines the percentages and individual masses of each isotope

8. Calculations
The average atomic mass is calculated by the percent of each isotope’s mass:
(mass) (%) +
(mass) (%) …

9. Practice Problem 1
Boron has two isotopes: Boron-10 and Boron-11. In nature 19% of Boron is Boron-10 and 81% is Boron- 11.

10. Answer
(0.19 x 10) + (0.81 x 11) = amu

11. Practice Problem 2
A new element, Tyserium (Ty) has recently been discovered on Mars and consists of two isotopes. One isotope has a mass of 331 amu and is 35.0% abundant. The other isotope is 339 amu and is 65.0% abundant. What is the mass of Ty?

12. Answer
(331 x 0.35) + (339 x 0.65) = amu

13. Logic Problem #1
Copper has an average atomic mass of amu and only exists as Copper-63 and Copper-65. What is the isotopic mass of the most common isotope of Copper?

14. Answer
Copper – 63
**Average mass is closer to Copper - 63

15. Logic Problem #2
The relative atomic mass of chlorine is 35.5 amu. What does this tell you about the relative abundance of the two naturally occurring isotopes of chlorine, Chlorine-35 and Chlorine-37.

16. Answer
Chlorine – 35
**Answer is closer to Chlorine - 35

17. Check Yourself!
Make sure your calculated average mass is within the range of the given mass numbers
Rationalize your results
Check your answers on the periodic table

18. Candium Lab
Goal:
Find the average atomic mass of Candium

19. When you are done with the lab…
Clean up area
Come up to the elmo and post average atomic mass
Complete analysis questions
Start Average Atomic Mass HW