What is Atomic Mass?
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What is Atomic Mass?

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What is Atomic Mass? What is Atomic Mass? Presentation Transcript

  • Launch: 9/16
    • 4. How does atomic number vary throughout the periodic table?
      • a. it is fixed and does not change as you move across the periodic table
      • b. it decreases from left to right, and from top to bottom
      • c. it increases from left to right, and from top to bottom
      • d. it increases from right to left, and from top to bottom
    • 1. All atoms of an element have
      • a. the same number of protons.
      • b. the same number of neutrons.
      • c. the same number of electrons.
      • d. neither mass nor volume.
  • What is atomic mass? Mr. Heffner Chemistry 9/15/09
  • What is an element?
    • All atoms in a specific element have the same atomic number
      • Atomic number = # of protons
    • The periodic table is organized by increasing atomic number
  • What is atomic mass?
    • Atomic mass is…
      • the number of protons and neutrons in an atom
      • the number of particles in the nucleus
    • Mass = weight
      • So, atomic mass is the weight of an atom
      • Units = amu (atomic mass units)
  • What is an element? Atomic number Symbol Name Atomic mass
      • 4.00
      • 2
      • He
      • Helium
  • What is atomic mass?
    • Atomic mass vs. atomic number
    Mass Number
    • Protons + neutrons
    • Just protons
    • Weight of atom
    • What defines atom
    • On bottom
    • On top
    • Decimal
    • Whole-number
  • What is atomic mass?
    • How to calculate the number of neutrons
    • Atomic mass – atomic number = # of neutrons
    • How many neutrons does He (Helium) have?
    • 4 – 2 = 2 neutrons
    • How many neutrons does Li (Lithium) have?
    • 7 – 3 = 4 neutrons
  • Summary
    • Atomic mass is the number of protons and neutrons in an atom
    • Atomic mass – atomic number = # of neutrons
  • Foldable
    • Fold in half 3X, then unwrap and fold in windows
      • Cut with scissors
      • 3 hole-punch
    • Terms: only 2!
      • Atomic mass
      • Neutron (charge, mass, location)
    • Quiz yourself when finished
  • Practice Questions
    • Answer the following in complete sentences:
    • What is atomic mass?
    • How is atomic mass different from atomic number?
    • Draw and label the representation of C (Carbon) including atomic mass.
    • How many neutrons do the atoms of the following elements have?
      • N (Nitrogen)
      • Mg (Magnesium)
      • Au (Gold)
  • What is atomic mass?
    • Trend for atomic number
      • INCREASES from Left to Right
      • INCREASES from Top to Bottom
    • An exception to the rule!
      • Co (Cobalt) and Ni (Nickel)
      • The periodic table is organized by atomic number, so Co must come before Ni
  • What is an isotope?
    • What is going on here?
      • Why are there exceptions?
      • Why are atomic masses not whole numbers?
    • An isotope is…
      • an atom that has the same number of protons as other atoms of the same element, but has a different number of neutrons
      • the same atomic number, but a different atomic mass
  • What is an isotope?
    • Most elements have a few stable isotopes
      • Carbon-12, atomic mass = 12.00
      • Carbon-13, atomic mass = 13.00
      • Carbon-14, atomic mass = 14.00
    • Why is atomic mass a decimal?
      • Because it is an average of the masses of the naturally occurring isotopes
  • What is an isotope?
    • How to calculate the number of neutrons in isotope
    • Atomic mass – atomic number = # of neutrons
    • How many neutrons does Carbon-13 have?
    • 13 – 6 = 7 neutrons
    • How many neutrons does Carbon-14 have?
    • 14 – 6 = 8 neutrons
  • Summary
    • Atomic mass INCREASES from
      • Left  Right
      • Top  Bottom
    • Isotopes have a different number of neutrons
      • Atomic mass = average mass = decimal
    • Atomic mass – atomic number = # neutrons
  • Foldable
    • Fold in half 3X, then unwrap and fold in windows
      • Cut with scissors
      • 3 hole-punch
    • Terms: only 2!
      • Isotope
      • Trend for atomic number and atomic mass
    • Quiz yourself when finished
  • Practice Questions
    • Answer the following in complete sentences:
    • What is an isotope?
    • Why is Co placed before Ni on the periodic table?
    • Why is atomic mass a decimal and not a whole #?
    • What is the trend for atomic mass?
    • How many protons and neutrons are in:
      • K
      • P
      • Hydrogen-2
      • Oxygen-18
  • Exit Slip
    • 1. How many neutrons does Carbon-12 have?
      • a. 2
      • b. 6
      • c. 12
      • d. 18
    • 2. In general, how does atomic mass vary throughout the periodic table?
      • a. it is fixed and does not change as you move across the periodic table
      • b. it decreases from left to right, and from top to bottom
      • c. it increases from left to right, and from top to bottom
      • d. it increases from right to left, and from top to bottom
  • Exit Slip
    • 3. Which of the following is true for isotopes?
      • a. they change the identity of an atom to a different element
      • b. they have varying atomic numbers
      • c. they have varying atomic masses
      • d. they have varying numbers of electrons
    • 4. Why are atomic masses listed as decimals on the periodic table instead of whole numbers?
      • a. they are a weighted average of the naturally occurring isotopes
      • b. their units are grams/moles
      • c. they were measured with a balance that read to only two decimal places
      • d. none of the above
  • Exit Slip
    • 5. On the periodic table, why is Co (Cobalt) placed before Ni (Nickel) even though Ni has a higher atomic mass?
      • a. Nickel has one more proton
      • b. Cobalt has fewer electrons
      • c. Nickel has a few more electrons
      • d. Cobalt has a lower density
  • Homework
    • Finish Practice Questions
    • Finish Foldable
    • Textbook:
      • Pg. 86 Practice: #1, 2, 4
      • Pg. 89 Section Review: #2, 4, 6, 8