Review of the Periodic Table and its Trends

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Review of the Periodic Table and its Trends
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You must be able to read the table!
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I II
III IV V VI
VII VIII
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• The Periods and Valence Orbitals

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• The Groups with a Roman Numeral represent the
  Primary or A elements
• The others are the Transition Elements or B
  elements
• The Lathinides and Actinides are the Inner
  Transition Elements
• The Roman Numeral equals the Number of Valence e-
  for that Group
• Valence e- are those in the last Energy level (n)

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• Dmitri Mendeleev is given credit for developing
  the first periodic table based on atomic weight
  it allowed him to predict new elements.
• However, it was Henry Moseley who set it up using
  the atomic number (Z).

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The First Periodic Trend

• Atomic Radius This varies according to the
  distance of the valence e- to the nucleus
• Two factors affect atomic radius the valence
  shells n (energy level) and the
  attractions/repulsions that occur in the atom
  

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• Atomic Radius (and Ionic Radius) is measured in
  Angstroms or pm or nm
• 1 A 10-10 m 0.1 nm 100 pm
• Atomic Radius Decreases
• I
• n
• c
• r
• e
• a
• s
• e
• s

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• Atomic Radii are measured using
• rcov which measures from the nuclei
• rvdw van der Waals which is used for non-bonding
  noble (inert) gases
• See the charts handed out for actual radii

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Metal molecules form lattice structures cube
shaped crystals with an atom at each corner.
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2. Ionic Radius

• This measures the size of an ion in a crystal
  lattice structure
• rion increases if a negative ion (anion)
• and decreases with a positive ion
• (cation)
• This is easy to explain a cation has lost e-
  and an anion has gained them changing the radius

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3. Ionization Energy (EI)

• This is the energy needed to remove an e- from an
  atom and create a cation
• The 1st Ionization Energy is the lowest since it
  is removing an e- from the valence shell
• EI increases as you get closer to the nucleus due
  to an increase in the attraction (EMF)
• Measured in eV or KJ/mol
• 1 eV is the charge of one e-
• 1 eV 1.60217653 x 10-19 J 96.48538 KJ/mol

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• EI Increases
• D
• e
• c
• r
• e
• a
• s
• e
• s

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• EI decreases due to distance from the nucleus
  and due to the shielding or screening effect
• The Shielding Effect is due to the interference
  of inner e-s disrupting the forces of nuclear
  attraction on an outer e-
• This effect, the Z or Zeff measures the amount
  of nuclear attraction on any particular electron
• Z Z - s

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4. Electron Affinity (EA)

• EA is the measure of how capable an atom is in
  gaining an e- and becoming an anion (negative
  ion)
• When an e- is gained, a quanta of energy is
  released as a photon or gamma particle
• This trend really centers on Group VI and VII
• Only Group VI has a 2nd EA
• Measured in kJ/mol or - eV

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• E A Increases
• D
• e
• c
• r
• e
• a
• s
• e
• s

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• 5. Electronegativity (?) or (EN)
• This is the power of an atom to attract e- and
  thus, form bonds
• There are several scales used to determine
• EN
• 1. The Pauling Scale ranges from 0.7 to 4.0
• The difference in EN between two atoms will
  determine what type of bond has been formed
  (see the scale handed out in class)

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• 2. The Mullikan Scale
• Also called the Absolute EN Scale
• Uses the mean of the 1st EI and EA to measure
  bond attraction
• EN in eV 0.187 (EI EA / 2) 0.17
• EN in kJ./mol (1.97 x 10-3)(Mean) 0.19
• 3. Allred-Rochow EN Scale
• EN is related to charge experienced on surface of
  atom

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• Uses Slaters Rules to find Z
• EN 0.359 (Z / rcov2 ) .744
• 4. Allen EN Scale
• EN nsEs npEp
• ns np
• Es and Ep are an e- energies of the s and p
  orbitals in the valence shell
• Ns and np are the number of e- in these orbitals
• kJ/mol _____ x (1.75 x 10-3)
• eV _____ x (0.169)

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• EN Using the Pauling Scale

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• E N Increases
• D
• e
• c
• r
• e
• a
• s
• e
• s

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The End. . .
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