1. +1 +2 +1,2,3,4,5,6….. (varies) 0 -2-3 +3,( -5) +4,-4 +3 +2 Preferred element charges In NM +NM combinations, element charges are irrelevant. They are relevant for M +TM and TM +NM combos

2. +1 +2 +1,2,3,4,5,6….. (varies) 0 -2-3 +3,( -5) +4,-4 +3 +2 Preferred element charges In NM +NM combinations, element charges are irrelevant. They are relevant for M +TM and TM +NM combos

3. The Big picture, Part 4 What does Dalton’s atom look like ?? What’s in the atomic box ?

4. The evolving inside picture of the atom (2.4-2.5) Philosophical Magazine 44, 295 (1897) Philosophical Magazine Series 6, 21, 669-688 (1911) Thomson Model 1897 Philosophical Magazine Series 6 26. 1-25 (1913) Bohr Model 1913

5. Dimensions of the atomic model Nuclear radius ~10 -15 meters Electronic cloud radius ~ 10 -10 meters Electronic radius/Nuclear radius ~ 10 +5 ~ 100,000

6. Atom dimensions in familiar terms. Baseball as nucleus Old Yankee Stadium, the Bronx Electrons start here (~2.4 miles past cheap seats) 3”

7. Nucleus(+) ~ dimension of Rutherford’s electronic cloud (-) (2.4 mile radius from baseball nucleus)

8. Subatomic pieceMass (g)Charge proton1.67*10 -30 neutron 1.67*10 -30 electron 9.11*10 -34 Masses of subatomic pieces (table 2.1, p. 46) + 0 - In neutral atoms # protons = # electrons

9. Proton mass Electron mass Weighs ~ 2000 eggs

10. Volume comparison Nuclear volume= 1 pea (~0.065 cm 3 ) Electron cloud volume ~ volume of water in Honeoye Lake, NY (10 15 times pea volume) The electron cloud volume is 10 15 times bigger than the nuclear volume

11. . All atoms of a given element have the same proton count. Atoms of different elements have different proton counts. Modern View of Elements (p. 54) Modern twist: a given element can have different neutron counts in the nucleus (isotopes) and still be the same chemically=> same element can differ in weight !

12. “ All atoms of a given element weigh the same” BOYLE & DALTON WERE WRONG (A LITTLE) …THEY didn’t know about isotopes and neutrons … but it can be forgiven…in 1805 equipment was little better than kitchen ware…. Dalton’s measured massCorrect average mass C N O Na 12 14 16 23 12.01 14.01 15.99 22.99

13. Atomic symbols p = atomic number (Z) defines element p + n = mass number=M (several choices for an element) p = e in neutral atom Isotope = element with specific count of n Z p M How to represent an isotope (p. 46)

14. Neon Isotopes Proton count (p + ) neutron count (n o ) p + + n o 101020 10 11 21 101222 Isotope symbol ? 20 Ne 10 21 Ne 10 22 Ne 10 21 Ne Alternative symbol (drop p…)

15. More Examples with alternate symbol: Boron 10 ( 10 B)= 5 p + 5 n Boron 11 ( 11 B) = 5 p + 6 n Hydrogen 1 ( 1 H) = 1 p + 0 n Hydrogen 3 ( 3 H) = 1 p + 2 n (tritium) Copper 63 ( 63 Cu) = 29 p + 34 n Copper 65 ( 65 Cu) =29 p + 36 n

16. How many neutrons in 37 Cl ? A.37 B.18 C.20 D.21

17. What is the symbol for an element with 35 protons and 46 neutrons ? A. 81 Br B. 81 Pd C. 81 Tl D. 81 Kr

18. ATOMIC BOOKKEEPING. 12 0 31150 17O910 Atomic # mass# symbol #p + #n o #e - atom charge 12 2412Mg 15 16P 88-2 Pertinent section of Periodic table

19. 20100 714 Fe300 171819 10 26 56 35 Ne N Cl 10 Atomic # mass# symbol #p + #n o #e - atom charge 7 26 17 10 7 8 26 -2 ATOMIC BOOKKEEPING (cont.) Brain toss variant…. Let’s go down a column left to right…. 1 mole buck/right answer with explanation

20. 6 C 12.01 12 O C 6 Periodic table entry for `average’ atom of C Nuclear notation for specific isotope of C Average atomic mass (not mass number ??) Atomic # = p Mass #= n + p Atomic # = p charge The Chemist’s element vs. the Physicist’s element Chemist’s elementPhysicist’s element

21. Why the chemist’s C lists 12.01 and not 12 # p # n mass # caught out of 100 C atoms 66 99 Imagine `fishing’ out 100 atoms of Carbon from a sample of graphite (pure carbon). What would you catch ? 12 6 713 1 Both kinds isotopes of C act exactly the same, chemically so chemists just average the masses Average mass of each C= 99*12 + 1*13 100 = 12.01

22. Average mass = of each C 99*12 + 1*13 100 = 12.01 = 99 *12 + 1 * 13 100 100 Averages Written As Sums Of Fractional Contributions =f 12 *12 + f 13 *13 f m = fraction of C atoms with mass M

23. Averages written as sums of % contributions = 99 *12 + 1 * 13 100 100 Average mass of each C =(99 % *12 + 1% * 13) 100 = (P 12 *12 + P 13 *13) 100 P m = % of C atoms with mass M

24. Take home lesson AV. MASS =f 1 *m 1 +f 2 *m 2 +….. Or, from % abundances P k and m k so: AV. MASS =P 1 *m 1 +P 2 *m 2 +….. 100 : Average mass is computable from fractional abundances f k and m k so:

25. In- class example with mercury: Compute the average mass of Hg from abundance data 1881 3144 5720 2492 5555 1246 Sum= 20057

26.  Average mass of Hg =20057 =200.57 100 AV. MASS =P 1 *m 1 +P 2 *m 2 +….. 100

27. One more `U-Do-it’ Example: Boron 11 B 81% 10 B 19% Isotope P= % abundance Average B mass ??? =81*11 + 19*10 100 AV. MASS =P 1 *m 1 +P 2 *m 2 +….. 100 =10.81