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Isotopes

0. Isotopes. 0. A quick review of the atom. completely different atom. Identity of the atom. Charge. Ion. Mass. Isotope. They are atoms of the same element that have different numbers of neutrons. 0. What Are Isotopes ?. It ’ s just a change in the neutrizzle fo shizzle!!!.

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Isotopes

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  1. 0 Isotopes

  2. 0 A quick review of the atom completely different atom Identity of the atom Charge Ion Mass Isotope

  3. They are atoms of the same element that have different numbers of neutrons. 0 What Are Isotopes? It’s just a change in the neutrizzle fo shizzle!!!

  4. Hydrogen has 3 isotopes There are 3 different “versions” of a hydrogen atom 0 An Example Note how the number of protons never change!!!

  5. Hydrogen has 3 isotopes There are 3 different “versions” of a hydrogen atom 0 An Example Having more neutrons increases the mass

  6. Hydrogen has 3 isotopes There are 3 different “versions” of a hydrogen atom 0 An Example Mass number = 1 Mass number = 3 Mass number = 2

  7. 0 Why does The atomic mass on the periodic table have so many decimal Places? 6 C 12.01115 13 Al 26.982 10 Ne 20.180

  8. 0 Atomic mass 1 H 1.00797 This atomic mass is the one number that best represents the mass of all three versions of hydrogen.

  9. 0 Atomic mass 1 H 1.00797 No atom of hydrogen anywhere in the universe actually has this mass.

  10. 0 Atomic mass 1 H 1.00797 This number is a “weighted” average of the masses of every isotope of hydrogen

  11. 1. First, you have to know the mass of each isotope 2. Second, you have to know the percent abundance*of each isotope *see next slide 0 Calculating a “weighted” average

  12. Percent abundance is how often that particular isotope occurs in a sample of the element 0 Percent abundance? A sample of magnesium collected anywhere in the universe will contain three isotopes of magnesium. Sample of Magnesium

  13. These are the percent abundances of each isotope of magnesium 0 Percent abundance? 78.90% of this magnesium will be the isotope named “magnesium 24” 10.00% of this magnesium will be the isotope named “magnesium 25” Sample of Magnesium 11.10% of this magnesium will be the isotope named “magnesium 26”

  14. This data will be provided to you in problems or you will be given a table where you can look it up. 0 Percent abundance? 78.90% of this magnesium will be the isotope named “magnesium 24” 10.00% of this magnesium will be the isotope named “magnesium 25” Sample of Magnesium 11.10% of this magnesium will be the isotope named “magnesium 26”

  15. The formula (Mass of isotope #1)(percent abundance) 100 (Mass of isotope #2)(percent abundance) 100 (Mass of isotope #3)(percent abundance) 100 0 Calculating a “weighted” average

  16. 0 Calculate the atomic mass of magnesium From the given data

  17. Using the formula for calculating a weighted average 23.985045(.7890) +24.985839(.1000) +25.982595(.1110) 24.306852 amu’s 0 Calculating the Atomic mass of magnesium Since its a “weighted” average this number has more influence since this mass occurs 79% of the time It’s NOT just a straight average where you add the masses and divide by 3 Note how the % abundances were converted to decimals (just divide each by 100)

  18. Try another example…

  19. 0 Calculate the Atomic Mass of Chromium

  20. 49.946046(0.0435) 51.940510(0.8379) + 52.940651(0.0950) 53.938882(0.0236) 51.995926 amu’s 0 Calculate the atomic mass of chromium

  21. 0 Terms associated with isotopes Vocabulary review

  22. Atomic number = the number of protons • It’s the same as the element’s position on the periodic table • For example, carbon is the 6th element on the table, so its atomic number is 6 which means it has 6 protons (and 6 electrons if it’s a neutral atom) 0 Vocabulary review

  23. Atomic mass = the “weighted” average mass of all the different isotopes of an atom • This is the “weird” number on the periodic table that usually has a bunch of places past the decimal point 0 Vocabulary review

  24. Mass number = the sum of protons + neutrons • This one kind of makes sense because the electrons essentially don’t have any mass • This HAS to be a whole number because you can’t have part of a proton or neutron • Mass number is NOT given on the periodic table 0 Vocabulary review

  25. What is the mass number of a carbon atom that has 6 neutrons? 7 neutrons? • How many neutrons does a nitrogen atom have if its mass number is 14? • How many neutrons does a chlorine atom have if its mass number is 36? • What is the atomic number of neon? • What is the atomic mass of neon? 0 Let’s Practice Those Terms…

  26. 12 and 13 • 7 • 19 • 10 • 20.180 amu’s 0 Answers

  27. 0 A shorthand way to write isotopes AXZ Notation for Isotopes

  28. AXZ 0 A Short Way to Write Isotopes “A” is the symbol for Mass Number (#protons + #neutrons) “Z” is the symbol for Atomic Number (# of protons) “X” will be the symbol of the element

  29. Jay - Z Yo! If you’re doin’ chem problems I feel bad for you son…. I got 99 problems, and here’s the first one….HIT ME!!!!

  30. Write aXz notation for an isotope that has 17 protons and 18 neutrons. Problem #1

  31. Write aXz notation for an isotope that has 17 protons and 18 neutrons. 35Cl17 Problem #1

  32. Write aXz notation for an isotope that has 19 protons and 21 neutrons. Problem #2

  33. Write aXz notation for an isotope that has 19 protons and 21 neutrons. 40K19 Problem #2

  34. Write aXz notation for an isotope that has 15 protons, 18 electrons, and 16 neutrons. Problem #3

  35. Write aXz notation for an isotope that has 15 protons, 18 electrons, and 16 neutrons. 31P3-15 Problem #3 This isotope is also an ion!!!

  36. How many protons, electrons, and neutrons are in this isotope? 41Ca2+ 20 Problem #4

  37. How many protons, electrons, and neutrons are in this isotope? 41Ca2+ 20 20 protons, 18 electrons, 21 neutrons Problem #4

  38. How many protons, electrons, and neutrons? • 56Fe2+26 • 27Al3+13 • 79Se2-34 More examples

  39. How many protons, electrons, and neutrons? • 56Fe2+26 26, 24, 30 • 27Al3+13 13, 10, 14 • 79Se2-34 34, 36, 45 More examples

  40. Write aXz notation for: • Isotope with 21 protons, 18 electrons, and 24 neutrons • Isotope with 53 protons, 74 neutrons, and 54 electrons More practice

  41. Write aXz notation for: • Isotope with 21 protons, 18 electrons, and 24 neutrons 45Sc3+21 • Isotope with 53 protons, 74 neutrons, and 54 electrons 127I-53 More practice

  42. 35Cl17 is the same as 3517Cl Might also see “Cl-35” or “chlorine-35” Different Forms of AXZ

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