1. Candium Average Atomic Mass

2. Lesson Frame I can calculate a weighted average to determine average atomic mass By using candy as an isotope in a guided laboratory activity I will know I have learned this when I can find the isotopic composition of an element and use it to calculate the average atomic mass.

3. Engage Why does Oxygen have a mass of 15.999 instead of 16 on the periodic table?

4. Explore 1.Obtain a sample of the element “Candium”. 2.Sort through and separate the different “isotopes” of “Candium”. Count the number of each “isotope” and mass each type of “isotope”. Record the information on your data table. 3.Calculate the average atomic mass of your sample.

5. Candium Data Table M&MSKITTLESTOTALS Number of isotope Mass of isotope Ave Mass Mass/# isotope Percent isotope (# isotope/ total #) x 100 100 Relative abundance (# isotope/ total #) 1.00 Relative mass ( Relative abundance x Ave Mass ) Average Atomic Mass Total of Relative mass

6. Calculations Number of isotope Mass of isotope Ave Mass = Mass/# isotope Percent isotope =(# isotope/ total #) x 100 Relative abundance = (# isotope/ total #) Relative mass= Relative abundance x Ave Mass Average Atomic Mass = Total of Relative mass

7. Explain Atomic Mass on the Periodic Table 11 Na 22.99 Atomic Number Symbol Atomic Mass

8. Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom. Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = 26.4 100 35.5 37 x 24.5 = 9.07 100 Explain - Atomic Mass

9. Example of an Average Atomic Mass Method # 2 Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 0.755 = 26.4 37 x 0.245 = +9.07 35.47 =35.5

10. Elaborate The isotopes of magnesium (and percent abundance) are Mg-24 (79.0%), Mg-25 (10.0%), and Mg- 26 (11.0%). Calculate the average atomic mass.

11. Evaluate Pick one topic below and use 2 paragraphs to support your answer. – Explain how Thomson’s cathode ray tube experiment worked and what it proved. – Explain how Rutherford’s gold foil experiment worked, and what it proved. – Describe the difference between Carbon- 12 and carbon-14.