Counting pieces
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Counting pieces Presentation Transcript

  • 1. Chapter 4 Foundations Counting the Pieces.
  • 2. Counting the Pieces
    • Atomic number = number of protons
    • # Of protons determines kind of atom
    • The same as the number of electrons in the neutral atom
    • Mass number = the number of protons + neutrons
      • Sum of all the things with mass
  • 3. Isotopes
    • Dalton was wrong.
    • Atoms of the same element can have different numbers of neutrons.
      • Since neutrons are heavy the two atoms have different mass numbers.
      • Called isotopes.
      • Two isotopes of sodium. Notice different # of N 0.
  • 4. Symbols
    • Contain the symbol of the element, the mass number and the atomic number
  • 5. Symbols
    • Contain the symbol of the element, the mass number and the atomic number
    X Mass number Atomic number
  • 6. Symbols
    • Find the
      • Number of protons
      • Number of neutrons
      • Number of electrons
      • Atomic number
      • Mass number
    F 19 9
  • 7. Symbols
    • Find the
      • number of protons
      • number of neutrons
      • number of electrons
      • Atomic number
      • Mass Number
    Br 80 35
  • 8. Symbols
    • if an element has an atomic number of 34 and a mass number of 78 what is the
      • number of protons
      • number of neutrons
      • number of electrons
      • Complete symbol
  • 9. Symbols
    • if an element has 91 protons and 140 neutrons what is the
      • Atomic number
      • Mass number
      • number of electrons
      • Complete symbol
  • 10. Symbols
    • if an element has 78 electrons and 117 neutrons what is the
      • Atomic number
      • Mass number
      • number of protons
      • Complete symbol
  • 11. Naming Isotopes
    • Put the mass number after the name of the element
    • Carbon- 12
    • Carbon -14
    • Uranium-235
  • 12. Atomic Mass
    • How heavy is an atom of oxygen?
    • There are different kinds of oxygen atoms.
    • More concerned with average atomic mass.
    • Based on abundance of each element in nature.
    • Don’t use grams because the numbers would be too small.
  • 13. Measuring Atomic Mass
    • Unit is the atomic mass unit (amu).
    • One twelfth the mass of a carbon-12 atom.
    • Each isotope has its own atomic mass we need the average from percent abundance.
  • 14. Calculating Averages
    • You have five rocks, four with a mass of 50 g, and one with a mass of 60 g. What is the average mass of the rocks?
    • Total mass = 4 x 50 + 1 x 60 = 260 g
    • Average mass = 4 x 50 + 1 x 60 = 260 g 5 5 5
    • Average mass = 4 x 50 + 1 x 60 = 260 g 5 5 5
  • 15. Calculating Averages
    • Average mass = 4 x 50 + 1 x 60 = 260 g 5 5 5
    • Average mass = .8 x 50 + .2 x 60
    • 80% of the rocks were 50 grams
    • 20% of the rocks were 60 grams
    • Average = % as decimal x mass + % as decimal x mass + % as decimal x mass
  • 16. Atomic Mass
    • Calculate the atomic mass of copper if copper has two isotopes. 69.1% has a mass of 62.93 amu and the rest have a mass of 64.93 amu.
  • 17. Atomic Mass
    • Magnesium has three isotopes. 78.99% magnesium 24 with a mass of 23.9850 amu, 10.00% magnesium 25 with a mass of 24.9858 amu, and the rest magnesium 26 with a mass of 25.9826 amu. What is the atomic mass of magnesium?
    • If not told otherwise, the mass of the isotope is the mass number in amu
  • 18. Atomic Mass
    • Is not a whole number because it is an average.
    • Are the decimal numbers on the periodic table.
  • 19. Atoms and ions
    • Atoms are electrically neutral
    • Same number of protons and electrons
    • Ions are atoms, or groups of atoms, with a charge
    • Different numbers of protons and electrons
    • Only electrons can move
    • Gain or lose electrons
  • 20. Anion
    • A negative ion
    • Has gained electrons
    • Non metals can gain electrons
    • Charge is written as a super script on the right
    F -1 Has gained one electron O -2 Has gained two electrons O + 2e -  O 2- F + e -  F -
  • 21. Cations
    • Positive ions
    • Formed by losing electrons
    • more protons than electrons
    • metals form cations
    K +1 Has lost one electron Ca +2 Has lost two electrons K  K + +e - Ca  Ca 2+ +2e -