Hodgepodge Notes

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Finding An Isotopic Mass. A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?. LecturePLUS Timberlake. 2. Okay ... So how do we get our values?. We know:Boron ? 10 is 10.00amuBoro

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Hodgepodge Notes

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1. Hodgepodge Notes % Abundance Calculations Bohr Models Lewis Dot Models LecturePLUS Timberlake 1

2. Finding An Isotopic Mass A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope? LecturePLUS Timberlake 2

3. Okay ... So how do we get our values? We know: Boron – 10 is 10.00amu Boron – 11 is 11.00amu The average of both is 10.8 amu LecturePLUS Timberlake 3

4. How do we find our formula from what we know already? We know the avg mass formula Avg mass = [ % (weight) ] + [ % (weight) ] 100 100 What information are we missing from this formula? So we say X is one % for isotope 1 and (1-X) is the % for isotope 2 4

5. Our formula is... Avg atomic mass = x (atomic mass of x) + (1-x) (atomic mass 1-x) For Boron that means 10.8amu = x (10amu) + (1-x) (11amu) 5

6. Solve for X: X (10.0) + (1 - X )(11.0) = 10.8 Multiply through by 100 10.0 X + 11 - 11.0X = 10.8 Solve for X -1x + 11 = 10.8 -11 -11 -1x = -.20 6

7. Practice Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass) LecturePLUS Timberlake 7

8. Solution AT8 Solution X = 70% LecturePLUS Timberlake 8

9. No lets model some atoms We will draw Bohr models and Lewis dot structures LecturePLUS Timberlake 9

10. Bohr diagrams To draw them you must know the # of protons, neutrons, and electrons (2,8,8,2 filling order) Draw protons (p+), (n0) in circle (i.e. “nucleus”) Draw electrons around in shells

12. What about isotopes? Draw a Bohr diagrams for the two Li isotopes. A- The atomic # of an element doesn’t change Although the number of neutrons can vary, atoms have definite numbers of protons.

13. 6Li 7Li

14. Bohr on the PT

15. Lewis Dot Models Octet Rule – atoms with 8 electrons are stable Steps Find the element on the periodic table What is the group number? Fill up the dots in a circle LecturePLUS Timberlake 15

16. What do you notice about the dot models?

17. Your Atomic theory project pt 2 Part 1 was create a time line of the development of the atomic theory. Part 2 is now, there is additional research on your part here. You must add in the following: Mosley, Dmitri Mendeleev, James Chadwick, Madame Curie, Max Planck, Erwin Schrodinger, the Double Slit experiment, Fermilab, Cern, String Theory, Brian Greene. You must also take one major culture apart from Europe during the time period of 1200 – 1700 and describe what was going on in that part of the world in terms of scientific advancement. What do these people/things tell us about the structure of matter? How has this changed or how is it expected to change our understanding of matter? While Europe was going through and coming out of the “Dark Ages” and into the Renaissance, what was happening in another major culture that was not experiencing the same turmoil?

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