STAAR Chemistry Review Topic: Atomic Structure

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STAAR Chemistry Review Topic Atomic Structure

• TEKS 6 The student knows and understands the
  historical development of atomic theory. 6A - E

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Student Expectation (SE)

• 6A understand the experimental design and
  conclusions used in the development of modern
  atomic theory, including Dalton's Postulates,
  Thomson's discovery of electron properties,
  Rutherford's nuclear atom, and Bohr's nuclear
  atom

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• INDEX CARD TIME!
• TITLE Daltons Four Postulates About The Atom
• FRONT Describe each of the four postulates
  Dalton proposed about the atom
• BACK Which of these are considered incorrect
  today?

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Mini Review Daltons Atom

• John Daltons Postulates about the atom include
• Elements are made of small, indivisible particles
  called atoms
• All atoms of a given element are identical
• Atoms of a given element are different from those
  of any other element and have different atomic
  masses.

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Mini Review Daltons Atom

• 4. In a chemical reaction, atoms of one element
  combine in whole number ratios with atoms of
  different elements. Chemical reactions rearrange
  atoms but do not change atoms to new elements.
• Today we know that atoms of the same element are
  not necessarily identical because they can
  contain different numbers of neutrons (isotopes)!

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• INDEX CARD TIME!
• TITLE JJ Thomson and The Electron
• FRONT Which experiment lead to the discovery of
  the electron? Explain how the experimental
  evidence demonstrated the existence of the
  electron.
• BACK Draw a sketch of what
• Thompson thought the atom
• looked like.

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Mini-Review - Electrons

• JJ Thomson s cathode ray experiment
• lead to the discovery of the electron. This
  experiment involved glass tubes containing gas at
  low pressure with electrodes at each end. When
  the electrodes were connected to an electric
  current a cathode ray was produced.

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Mini-Review - Electrons

• The cathode rays were attracted to positively
  charged metal plates, and repelled by negatively
  charged plates, so Thomson hypothesized these
  rays were beams of negatively charged,
  particles, the electron!

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Mini-Review - Electrons

• Tompsons model of the atom was that the atom was
  like a blueberry muffin - the batter is the
  positively charged region of the atom, with
  negative blueberries scattered throughout.
• Tompson called it the plum-pudding model, after a
  gross British dessert with plums randomly
  scattered in a cake. Blueberry muffins are easier
  to remember, since youve seen one before!

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• INDEX CARD TIME!
• TITLE Rutherford and the Nucleus
• FRONT Which experiment lead to the discovery of
  the nucleus? Explain how the experimental
  evidence demonstrated the existence of the
  nucleus.
• BACK Draw a sketch of what
• Rutherford thought the atom
• looked like.

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Mini-Review - Rutherford

• Rutherford conducted the gold foil experiment to
  test Thomsons model of the atom. Rutherford
  shot a beam of positively-charged, high energy
  alpha particles through a piece of gold foil
  (like aluminum foil, but made of gold).
  Rutherford thought that if the positive charge
  was distributed evenly throughout the atom, most
  of the alpha particles would pass straight
  through without deflection.

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• However, a small portion of the atoms were
  actually deflected back toward the source of the
  alpha particles, and did not pass through the
  foil. Rutherford hypothesized that the alpha
  particles struck a small, dense region of
  positive charge at the center of the atom called
  the nucleus.
• Student pictures should incorporate a nucleus of
  positive charge in the center of the atom.
  Neutrons hadnt been discovered yet!

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Student Expectation (SE)

• 6B understand the electromagnetic spectrum and
  the mathematical relationships between energy,
  frequency, and wavelength of light

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• INDEX CARD TIME!
• TITLE The Electromagnetic Spectrum
• FRONT What is it? What is the highest energy
  item on the right of spectrum, and the lowest
  energy item on the left?
• BACK Which color of light is the
• Highest energy? The lowest?

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Electromagnetic Spectrum

• The electromagnetic spectrum is a visual
• representation of all the wavelengths and
  frequencies of electromagnetic radiation. Notice
  that the visible spectrum of light makes up only
  a small portion of the entire electromagnetic
  spectrum. (See diagram next slide). From low to
  high energy/frequency the electromagnetic
  spectrum contains radio waves, microwaves,
  infrared, visible light, ultraviolet, X-rays, and
  gamma rays

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Mini-Review

• Low energy
  High energy

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Student Expectation (SE)

• 6C calculate the wavelength, frequency, and
  energy of light using Planck's constant and the
  speed of light

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• INDEX CARD TIME!
• TITLE Calculating energy, frequency, and
  wavelength
• FRONT What are the two equations needed to
  calculate the energy, frequency, or wavelength of
  light ?
• BACK What are the given constant
• Values for the two equations?

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Mini-Review Light Calculations

• Equation c f x ?
• Where c speed of light, f frequency,
• ? wavelength
• Units for frequency are hertz (Hz)
• Units for wavelength are nanometers (nm) for
  light, but can be a metric value of meters for
  other forms of electromagnetic radiation.
• Constant c 3.00 x 108 m/s

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Mini-Review Light Calculations

• E h x f
• Where Eenergy, h Plancks constant,
• f frequency
• Units for frequency are hertz (Hz)
• Units for energy are
• Constants h 6.626 x 10 -34 J/s

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Student Expectation (SE)

• 6D  use isotopic composition to calculate
  average atomic mass of an element

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• INDEX CARD TIME!
• TITLE Isotopes and Average Atomic Mass
• FRONT How do you calculate average atomic mass?
  
• Back What does average atomic mass represent?

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Average Atomic Mass

• Average atomic mass of an element is
• The average mass that is weighted based on the
  abundance of each of the atoms isotopes.
• To calculate any average atomic mass you need to
  know each isotope of the element, its percent
  abundance, and the mass of each isotope.

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Calculating Average Atomic Mass

1. Convert all percent abundance values into
   decimal form (divide by 100).
2. Multiply the atomic mass by the decimal percent
   abundance for each isotope.
3. Add the multiplied mass times abundance values
   for each isotope value together.
4. The unit for atomic mass is amu!

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Calculating Average Atomic Mass
Isotope Atomic Mass (amu) Relative Abundance Decimal Relative Abundance
Carbon-12 12.00 98.93 0.9893
Carbon-13 13.0033355 1.07 0.0107

• Carbon-12 12.00 amu x 0.9893 11.87 amu
• Carbon-13 13.0033355 x 0.0107 0.1391 amu
• Average Atomic Mass 11.87 0.1391 12.01 amu

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Student Expectation (SE)

• 6E express the arrangement of electrons in
  atoms through electron configurations and Lewis
  valence electron dot structures.

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• INDEX CARD TIME!
• FIRST Describe to your table partner how to do
  both regular and noble gas electron
  configurations.
• TITLE Electron configuration
• FRONT Write down the directions you just
  discussed for both types of electron
  configuration.
• BACK Describe where the S, P, D, and F blocks
  are on the periodic table

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Electron Configuration

• An electron configuration describes which
• atomic orbitals hold the atoms electrons.
  Electrons occupy the atomic orbitals with the
  lowest energies first. The easiest way to write
  an electron configuration is using the periodic
  table. You need to look at the period and blocks
  of the periodic table to fill in full electron
  configurations. See the diagram on the next
  page.

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Electron Configuration

• The electron configuration for hydrogen is 1s1
• The first number one indicates the principal
  energy level, the letter s indicates the sublevel
  and type of atomic orbital, and the superscript
  (exponent) 1 indicates the number of electrons in
  the s orbital.

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• INDEX CARD TIME!
• TITLE Lewis Dot Structures
• FRONT How do you know how many dots to draw on
  a Lewis Dot Structure?
• BACK Draw a Lewis Dot Structure for 8 elements
• (A Lewis Dot Structure
  for an element with 1, 2, 3, 4, 5, 6, 7, and 8
  v.e.s)

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Mini-Review

• You draw a dot for each valence
• electron an element has for a Lewis Dot
  Structure.
• See next slide for element examples

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Mini-Review
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• Review slide information directly from Texas
  STAAR Review and Practice by Pearson