1. 1. I have 22 neutrons and a mass of 40. 2. I have 37 protons and 39 electrons. 3. I have 22 neutrons and 19 protons.

2. At your atom letter, you will finish your Bohr model of an atom. You will move around the room clockwise once finished to look at everyone else’s atoms. Record p +, n o, e - for each. Hyphen notation Nuclear Notation Element – mass # Uranium - 238 238 92 U

3. Topic: Isotopesp. 35 Obj: understand the conclusions of Bohr’s nuclear atom. Use isotopic composition to calculate average atomic mass. ESQ: How are isotopes similar? Different? How do you calculate the average atomic mass of an isotope?

4. All LIES! Dalton’s Atomic Theory – the part that states that atoms of the same element are identical – is NOT always true

5. Isotopes are atoms of the SAME element that have DIFFERENT numbers of NEUTRONS and therefore different masses.

6. Example: There are 3 types of Hydrogen #p: #p: #p: #e: #e: #e: #n: #n: #n:

7. Isotope Notation #1 - Hyphen notation Element name – mass number Ex 1: Nitrogen-15  How many protons? ______  How many electrons? ______  How many neutrons? ______ 7 7 8

8. 2.) Nuclear Symbol Example 2: 238 Example 2: 238 92 92  How many protons? ______  How many electrons? ______  How many neutrons? ______ Isotope Notation U 92 146

9. NameSymbolMass Number #p#n#e Chlorine-37 35 Cl 17 14 C 6 Carbon-12 37 Cl 3717 2017 Chlorine-35 35 17 1817 Carbon-14 14 6 86 12 C12 6 6 6

10. Get out page 34 homework por favor… Put page 36 on the average atomic mass calculations. On page 35 (notes), skip a line and put a subtitle: AVERAGE ATOMIC MASS

11. ◦ An oxygen atom weighs 2.657 x 10 -22 g. This is difficult to use. Way too little!!! ◦ The atomic mass unit (amu) was developed for the purpose of making calculations easier. It’s kind of like “mole.” We made up these units to make the numbers make more sense. ◦ 1 amu = 1/12 th the mass of a Carbon-12 atom

12.  The average atomic mass is a WEIGHTED average of ALL of the isotopes for an element.  The average atomic mass of a sample of an element can be found on the periodic table ◦ Ex) Zinc = 65.39 amu

13.  The mass of one atom is not exactly the same as the average mass of many. ◦ Ex) 1 atom of Zinc  65.39 amu for mass #  p + + n o always equals a whole #

14. At Haltom, we average grades just like in math. Add up your grades and divide by the number of grades. This is a typical average. Daily – 50% 63 Major – 50%+74 137 / 2 = 68.5 In another school district, they calculate grades like this: Daily grades – 40% 63 Major grades – 60% 74 Here since they aren’t equal weights, the average is more influenced by the major grades since they count as a higher %. This kid actually gets a 69.6  70 for the six weeks!

15.  (% abundance x mass number isotope 1)  + (% abundance x mass number isotope 2)  + (% abundance x mass number isotope 3)  + etc.  = average atomic mass for the element DO NOT DIVIDE BY ANYTHING! This is not a regular average. Don’t forget to change the percentage to a decimal first!!! means how often it is found

16. Copper has two naturally occurring isotopes: copper-63 (69.17%) and copper-65 (30.83%). Calculate the average atomic mass of copper if the relative masses of the isotope are copper 63 (62.93 amu) and copper-65 (64.93 amu).

17. Cu-63 (0.6917 x 62.93 amu) Cu-65 + (0.3083 x 64.93 amu) 1) Change % to a decimal 2) Line up your info. 3) Use parentheses on calculator if you want to do it all at once without having to write it down for each isotope! May try to do it without them and check the order of operations. Some calculators know how to make this work even without the parentheses.

18. Cu-63 (0.6917 x 62.93 amu) Cu-65 + (0.3083 x 64.93 amu) Avg. mass = 63.55 amu * Notice average is always between the low & high amu but not necessarily in the middle.

20.  Naturally occurring boron is 80.20% boron-11 (atomic mass = 11.01 amu) and 19.80% of some other isotopic form of boron. What must the atomic mass of this second isotope be in order to account for the 10.81amu average atomic mass of boron? Round to the nearest hundredth.

22. 1. Gold 2. Tin 3. Arsenic 4. Lead 5. Beryllium 6. Bromine 7. Potassium 8. Chlorine 9. Sodium 10. Manganese 11. Ag 12. Hg 13. U 14. Fe 15. Cr 16. I 17. Pt 18. Cu 19. P 20. He

23.  An unknown element, Q, has an average atomic mass of 73.75 amu. The first isotope of Q has a mass of 72.99 amu and the second isotope has a mass of 74.99 amu. What are the percentages of each isotope?

25.  Remember…  X  1-x  Watch Sig Figs!!!  Open the container and I will hurt you… F!!!!