2. 3-3: Counting Atoms

3. Beaker Breaker 1.What was the name of Rutherford’s experiment? 2.What did Rutherford’s experiment discover? 3.My atomic number is 36..who am I?

4. Objectives Explain isotopes Define mass # and atomic # Given the identity of a nuclide, determine its # protons, neutrons & electrons

5. What is the same for all atoms on an element ? # protons Atomic number, Z = # protons in the nucleus of each atom of that element

6. ISOTOPES Atoms of the same element that differ in mass Have the same # protons but different # neutrons

7. Isotopes (con’t) Atomic # = # protons # protons determines the identity of the element # neutrons determines the isotope of the element (Another revision to Dalton’s Theory) Although isotopes differ in mass, they do NOT significantly differ in their chemical properties

8. Beaker Breaker 1.The_____________of an element is the number of protons in the nucleus of each atom of that element. 2.______________are atoms of the same element that have different masses. 3.________________number is the total number of protons and neutrons in the nucleus of an isotope.

9. Mass number: total number of protons and neutrons in the nucleus of an isotope # protons (At. #) + # neutrons Mass # Mass Number

10. NUCLIDE: particular kind of atom containing a definite number of protons and neutrons –ex. Carbon-14 Mass #, A - total # nucleons (particles that make up the nucleus --> protons and neutrons)

11. How many neutrons are in carbon-14? If: # protons (At. #) then: 6 + # neutrons + ? Mass # 14

12. How can you determine the # neutrons in an isotope? Mass # # protons + # neutrons - Atomic # - # protons # neutrons

13. Designating Isotopes Carbon–14 (name mass #) or…….. 14 C mass # element symbol. 6 atomic #.

14. Radium-226 ID the following: # protons # neutrons # electrons atomic symbol

15. Radium-226 ID the following: # protons Atomic # = 88 88 protons # neutrons 226-88=138 # electrons # protons = # electrons (neutral) 88 electrons atomic symbol 226 Ra 88

16. Beaker Breaker 1.How many protons, electrons, and neutrons are in an atom of bromine-80? 2.Write the nuclear symbol for carbon-13 3.Write the hyphen notation for the element that contains 15 electrons and 15 neutrons.

17. Homework

19. Atomic masses are VERY, VERY small…..too small to be measured in grams! We need another way to express “how much”

20. Electron = 9.10953 x 10 -28 g Proton = 1.67265 x 10 -24 g Neutron = 1.67495 x 10 -24 g

21. Scientists use a relative scale to describe atomic mass – Atomic Mass Units Carbon-12 nuclide is the standard Carbon-12 = 12 atomic mass units (amu) The mass of all nuclides is determined by comparing them to carbon-12

22. What is the value of 1 amu ?? If 12 amu = 1 carbon-12 atom, then… 1 amu = 1/12 the mass of a carbon-12 atom Since H = 1/12 the mass of carbon-12, then.. H = 1/12 ( 12 amu) = 1 amu O = 4/3 mass of carbon-12 = 4/3 (12amu) = 16 amu

23. If we round… proton = 1 amu neutron = 1 amu electron = 0 amu proton = 1.007276 amu neutron = 1.008665 amu electron = 0.0005486 amu

24. Atomic Mass Sum of subatomic masses in a atom –Carbon-12: 6 protons = 6 ( 1 amu) = 6 amu 6 neutrons = 6 ( 1 amu) = 6 amu 6 electrons = 6 ( 0 amu) = 0 amu 12 amu

25. Predict the atomic mass of oxygen-16 8 protons + 8 neutrons + 8 electrons = 8 amu + 8 amu + 0 amu = 16 amu How does this compare with the atomic mass value on Periodic Table?

26. Predict the atomic mass of uranium-234 92 protons + 142 neutrons + 92 electrons = 92 amu + 142 amu + 0 amu = 234 amu How does this compare with the atomic mass value on Periodic Table? 238 !!…why is it different?

27. Average Atomic Mass Weighted average of the atomic masses of the naturally occurring isotopes of an element

28. IF 40.% of the students living in Hershey have 2 telephones while 60.% of the students have 4 phones, what is the average # phones in Hershey homes? (0.40 x 2 phones) + (0.60 x 4 phones) 3.2 phones “weighted” average

29. What is the aver. atomic mass of the chlorine? IsotopeIsotope Mass (amu)% Abundance Chlorine-3534.9688575.771 Chlorine-3736.9659024.229

30. Average Atomic Mass = (isotope mass)(relative abundance[dec]) + (isotope mass)(relative abundance[dec]) (0.75771)(34.96885amu) + (0.24229)(36.96590amu) = 35.453 amu

31. Which isotope of hydrogen is the most abundant…? hydrogen-1 hydrogen-2 hydrogen-3 Hydrogen-1 (1.0079 = aver. atomic mass on chart)

32. Complete the following: Beaker Breaker ( not in packet) Isotope# protons#electrons#neutron Oxygen-16 29 34 Uranium-238

33. Complete the following: Isotope# protons#electrons#neutron Oxygen-16 8 8 8 Copper-63 29 34 Uranium-238 92 146

34. Objectives Define MOLE in terms of Avogadro’s # Define MOLE in terms of molar mass Use FLM to convert between grams, moles and # atoms/molecules

35. Relating MASS to # ATOMS

36. The Mole (mol) Amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon-12 (Avogadros #) Experimentally determined to 6.0221367 x 10 23 atoms 6.022 x 10 23

37. “Mole Things” Conversions

38. How many atoms are in 0.43 moles of copper? 0.43 mol Cu 6.02 x 10 23 atoms Cu = 11 mol Cu 2.6 x 10 23 atoms of Cu

39. How many moles are in 1.4 x 10 22 atoms of aluminum? 1.4 x 10 22 atoms Al 1 mole Al 1 6.02 x 10 23 atoms = 0.023 mol Al

40. Beaker Breaker Calculate the number of molecules in 1.058mole of H 2 O?

41. Molar Mass Mass of 1 mole of a pure substance Numerically equal to the atomic mass but expressed in GRAMS

42. What is the molar mass of the following: Potassium ? 39.098 g (or 39.098 g/mol) Nickel ? 58.693 g (or 58.693 g/mol)

43. What is the atomic mass of the following: Potassium ? 39.098 amu Nickel ? 58.693 amu

44. Gram- Mole Conversions

45. How many grams are needed to have 0.852 moles gold? 0.852 mol Au 196.97 g Au 1 1 mol Au = 168 g Au

46. How many moles are in 55 g of lead? 55 g Pb 1 mol Pb 1 207.2 g Pb = 0.26 moles Pb

47. How many moles are in 86.1 g sodium? 86.1 g ? mole Na = 1 ? g 86.1 g 1 mole Na = 1 22.99g 3.74 moles Na

48. How many atoms would be in 12.0 grams of carbon-12 ? If …atomic mass of carbon-12 = 12.0 amu (chart value) Then…12.0 g C = 1 mole (molar mass) And since…..1 mole = 6.022 x 10 23 atoms Then… 12.0 g carbon contains 6.02 x 10 23 C atoms

49. Beaker Breaker 1.How many moles are there in 5.04x10 3 atoms of Cu?

50. Gram #Atoms Conversions

51. How many atoms are in 54.21 g potassium? 54.21 g K 1 mole K 6.022 x 10 23 atoms K 1 39.098g K 1 mole K = 8.350 x 10 23 atoms K

52. How many grams are in 5.75 x 10 21 atoms of Mg? 5.75 x 10 21 atoms 1 mole 24.305 g 1 6.022 x 10 23 atoms 1 mole 0.232 grams Mg

53. Beaker Breaker How many grams are there in 780atoms of nickel?

55. MOLE definition movie D:\data\0030665841\student\ch07\sec03\qc02\h c207_03_q02fs.htm D:\data\0030665841\student\ch07\sec03\qc02\h c207_03_q02fs.htm