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Sub atomic heavyweights

Sub atomic heavyweights. Isotopes. ChemCatalyst. A chemist investigating a sample of lithium found that some atoms have a lower mass than other atoms. The chemist determined that the structures of the two types of atoms would be similar to the two drawings below. (cont.).

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Sub atomic heavyweights

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  1. Sub atomic heavyweights Isotopes

  2. ChemCatalyst A chemist investigating a sample of lithium found that some atoms have a lower mass than other atoms. The chemist determined that the structures of the two types of atoms would be similar to the two drawings below. (cont.) Unit 1 • Investigation III

  3. What is different about the two atoms? What is the atomic number of each atom? What is the mass number of each atom? Do you think they are both lithium atoms? Why or why not? (cont.) Unit 1 • Investigation III

  4. The Big Question How do isotopes of an atom account for the atomic weight of an element? Unit 1 • Investigation III

  5. WHAT IS AN ISOTOPE?

  6. Isotopes Atoms of the same element that have different numbers of neutrons Ex: Most hydrogen atoms have no neutrons. But a rare form of hydrogen atoms will have a neutron

  7. Differences in Isotopes • Different number of neutrons • Different mass values • Some isotopes are more stable (not radioactive)

  8. Similarities in isotopes • All isotopes of an element have the basically the same characteristics: Color Reactivity What elements they react with Conductivity How shiny or dull Etc…

  9. HOW TO WRITE THE NAME OF AN ISOTOPE

  10. Isotope names Two ways 1st: list the name or symbol of the element and the mass number of the isotope: Ex Uranium-237, U-238 (can use symbol) 2nd: Write symbol of element and place the mass number on top and the atomic number below Ex 12 C 6

  11. Weapon gets its energy from Pu-239

  12. Write both versions of the isotope names for each of the following: • Molybdenum (Mo) atom with 55 neutrons • Tungsten atom with a mass number of 183 • An atom of the most common isotope of Xenon

  13. Subatomic Heavyweights Work with a partner to complete the chart and compare answers to the questions in the handout

  14. Activity Goal: Complete the chart on back. Determine the average atomic weight for the 10 atoms shown (cont.) Unit 1 • Investigation III

  15. (cont.) (cont.) Unit 1 • Investigation III

  16. How did you find the atomic weight?

  17. Atomic weight The weighted average of the atomic masses of different isotopes taking into account their abundance

  18. Determining Atomic weight from % • Need to know the percentage of the element’s atoms that conform to each isotope Ex: 68% of Cu is Cu-63, 32% is Cu-65 To determine atomic weight: 1) convert % into decimal equivalent 2) multiply decimal to mass # 3) add resulting values (0.68)(63) + (0.32)(65) = 63.7 = atomic weight

  19. Try • Magnesium has 3 isotopes • 70% of atoms are Mg-24 • 29% of atoms are Mg-25 • 1.0% of atoms are Mg-26 • What is the atomic weight of Mg?

  20. Check in Predict the isotopes of Carbon, C. Which isotope is more abundant? How do you know?

  21. Most common isotopes • Look at atomic weight on PT • Most common isotopes are generally found by rounding the weight up OR down Ex: Os (Osmium) = 190.2 so The 2 most common isotopes are Os-190 and Os-191 Which is there more of?

  22. Do Handout together

  23. Complete chart Unit 1 • Investigation III

  24. Questions for section Label sketches in question 1 How do you average values?

  25. Answers to lab questions Fill in chart 2 different isotopes: Boron-10, Boron-11 2 atoms of Boron-10, 8 atoms of Boron-11 10, 11 amu, add protons and neutrons (10+11+11+11+11+10+11+11+11+11)/10 = 10.80 amu 10.80 compared to 10.81

  26. More answers to lab questions 6a) 2 different isotopes 6b) 20 Boron-10 and 80 Boron-11 6c) 20%, 80%

  27. Even more answers to lab questions 8) 3 isotopes 9) Argon-40 is the most common 10) 4 neutrons, because Lithium-7 is most common isotope

  28. Making Sense Explain why the atomic weights listed in the periodic table are not usually whole numbers. Unit 1 • Investigation III

  29. While the element iron is defined as being made up of neutral atoms with 26 protons and 26 electrons, not every iron atom has the same number of neutrons. Atoms that have the same number of protons but different numbers of neutrons are called isotopes. Notes (cont.) Unit 1 • Investigation III

  30. What we call the atomic weight on the periodic table is actually the average atomic mass of that element’s naturally occurring isotopes. Isotopes have similar chemical properties in that they combine with other elements to form similar compounds. Notes(cont.) (cont.) Unit 1 • Investigation III

  31. Atomic Weight is the weighted average of the atomic masses of different isotopes taking into account their abundance. (cont.) (cont.) Unit 1 • Investigation III

  32. (cont.) Unit 1 • Investigation III

  33. If you finish early Cu Has 2 naturally occurring isotopes 69% with 34 neutrons, 31% with 36 neutrons Calculate average atomic mass of Cu

  34. Isotopes of a single element exhibit similar properties in that they form similar compounds. Isotopes are referred to by their mass numbers. (cont.) Unit 1 • Investigation III

  35. Wrap-Up Elements may have anywhere from 2 to 10 naturally occurring isotopes. The atomic weight of an element listed on the periodic table is actually the average mass of the naturally occurring isotopes of that element. Isotopes have the same number of protons and electrons, but different numbers of neutrons. (cont.) Unit 1 • Investigation III

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