Monday, November 17th, 2014 HW= Unit 3 Review Problems #1-10 Objective: We will be able to calculate the average atomic mass of an element based on isotope abundance. Standard: IOD 401 Catalyst: According to Figure 2, which of the following minerals would most typically be found only in rocks of a medium grade? A. Muscovite B. Biotite C. Kyanite D. Plagioclase Classroom expectations: Wear Kenwood ID. Cell phones, music players, and headphones are put away. Food is disposed of or put away. Dressed appropriately. Notebook is out and you are ready for today’s class. Table of Contents: 11/17 Week 12 Catalyst Chart 71 11/17 Unit 3 Review (do NOT staple, turning in) 72 11/17 Notes: Calculating Average Atomic Mass/w Practice 73

Announcements Test THIS FRIDAY!!! Tutoring Tuesday and Wednesday THIS WEEK!! NO HELP AVAILABLE FROM MS. INGHAM THURSDAY!! There WILL BE a notebook check before Thanksgiving break!!

Agenda Catalyst/Announcements Homework Check/Review Notes: Calculating Average Atomic Mass Practice Problems Practice Wkst

Agenda Problems An isotope is the same atom (same amount of protons) with a different mass (different amount of neutrons) 14) The average atomic mass will be closer to 63 amu because the isotope with the mass of 63amu is more abundant. 15) 85.56 amu 16) 48.66 amu 17) 35.49 amu or 35.46 amu

Calculating Average Atomic Mass Pg 73

Isotopes Recall Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of Chlorine 35 Cl 37 Cl 17 17 Chlorine - 35 Chlorine - 37

Isotopes Recall Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons. Neon-20, neon-21, and neon-22 are three isotopes of neon, a gaseous element used in lighted signs. Comparing and Contrasting How are these isotopes different? How are they similar?

Isotopes Recall Isotope Protons Electrons Neutrons Nucleus Hydrogen–1 (protium) 1 Hydrogen-2 (deuterium) Hydrogen-3 (tritium) 2

Review: Check for Understanding Fluorine has an atomic number of 9. Write out the name of the isotope of fluorine that has 8 neutrons. Fluorine-17

Review: Check for Understanding Fluorine has an atomic number of 9. Write out the SYMBOL of the isotope of fluorine that has 10 neutrons. Mass #  19 F Atomic #  9

Review: Check for Understanding Three isotopes of chromium are chromium-50, chromium-52, and chromium-53. How many neutrons are in each isotope, given that chromium has an atomic number of 24? Chromium-50: 50-24 = 26 Chromium-52: 52-24 = 28 Chromium-53: 53-24 = 29

Average Atomic Mass What is average atomic mass? Average atomic mass is the weighted average of the atomic masses of the naturally occurring isotopes of an element The average mass on the periodic table is closest to the ISOTOPE of GREATEST abundance

Check for Understanding The average atomic mass of Carbon, C, is 12.01 amu. Predict which isotope has the greatest percent abundance based upon the average atomic mass. Carbon – 10 Carbon – 12 Carbon – 13 Carbon -- 14

Calculating Average Atomic Mass To calculate the atomic mass of an element, multiply the mass of each isotope by its percent abundance, expressed as a decimal, and then add the products. Reminder: To express a percent as a decimal move the decimal 2 places to the left ex: 89.97% = 0.8997

Calculating AverageAtomic Mass (Mass isotope # 1) (% Abundance as a decimal) + (Mass isotope # 2 ) ( % Abundance as a decimal) (Mass isotope # 3) ( % Abundance as a decimal ) + …..

Calculating a Weighted Average Example A box contains two size of marbles. If 25.0% have masses of 2.00 g and 75.0% have masses of 3.00 g what is the weighted average? (.250) (2.00) + (.750) (3.00) = .500 + 2.25 = 2.75g

Whiteboard Practice Show all of your work when completing the problem. DO NOT hold up your board until told to do so.

Practice Problem #1 EXAMPLE Boron has two isotopes: B-10 (mass 10.013 amu) 19.8% abundance B-11 (mass 11.009 amu) 80.2% abundance Calculate the average atomic mass. (.198) (10.013) + (.802) ( 11.009) = 1.98 amu + 8.83 amu = 10.81 amu

Calculating Average Atomic Mass Calculate the average atomic mass of Mg. Isotope 1 - 23.985 amu (78.99%) Isotope 2 - 24.986 amu (10.00%) Isotope 3 – 25.982 amu (11.01%) (23.985)(.7899)+(24.986)(.1000)+(25.982)(.1101) 18.95 amu + 2.499 amu + 2.861 amu = 24.31 amu

Average Atomic Mass Helium has two naturally occurring isotopes, He-3 and He-4. The atomic mass of helium is 4.003 amu. Which isotope is more abundant in nature? Explain. He-4 is more abundant in nature because the atomic mass is closer to the mass of He-4 than to the mass of He-3.

Practice Worksheet Complete the problems on the practice worksheet making sure to show all work when necessary.