Periodic Trends (p. 342 - 363)

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Periodic Trends(p. 342 - 363)

• Ch. 4 11 - The Periodic Table

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A. Chemical Reactivity

• Similar Properties in Groups/Families
• Similar valence e- within a group result in
  similar chemical properties

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A. Chemical Reactivity

• Alkali Metals
• Alkaline Earth Metals
• Transition Metals
• Halogens
• Noble Gases

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B. Other Periodic Properties

• Atomic Radius
• size of atom

• First Ionization Energy
• Energy required to remove one e- from a neutral
  atom.

• Melting/Boiling Point
• Density

• Electronegativity
• Ability of one atom to attract another atoms
  electrons

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C. Atomic Radius - Trends

• Atomic Radius

K
Na
Li
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C. Atomic Radius

• Atomic Radius

• Increases to the LEFT and DOWN

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C. Atomic Radius

• Why larger going down (in a group)?
• Shells - Higher energy levels have larger
  orbitals
• Shielding - core e- block the attraction between
  the nucleus and the valence e-
• Why smaller to the right (across a period)?
• Increased nuclear charge without additional
  shielding pulls e- in tighter

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D. Ionization Energy - Trends

• First Ionization Energy the energy required to
  remove one e- from a neutral atom.

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D. Ionization Energy

• First Ionization Energy

• Increases UP and to the RIGHT

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D. Ionization Energy

• Why opposite of atomic radius?
• In a group In small atoms, e- are close to the
  nucleus where the attraction is stronger. In
  larger atoms, e- are farther away from nucleus.
• Across a period, increased nuclear charge
  (protons) tugs harder on e-

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E. Melting/Boiling Pt. Density- Trends

• Melting/Boiling Point and Density

• Generally highest in the middle of a period and
  highest at the bottom of a group

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F. Electronegativity - Trends

• Electronegativity

• A measure of the ability of an atom to attract
  electrons a tug-of-war when bonding with
  other elements.

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F. Electronegativity

• Electronegativity

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F. Electronegativity

• Decreases as you move down a group.
• Shielding Though there are more protons as you
  move down group, the core e- block the possible
  attraction bet. the nucleus and the e-
• Shells The outer energy level is farther away,
  so attractive force of nucleus is smaller
• Increases (generally) as you move across a
  period.
• More protons in nucleus with the same sheilding
  attractive force is greater

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G. Ionic Radius

• Ionic Radius

• Cations ()
• lose e-
• smaller

• Anions ()
• gain e-
• larger

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H. Summary Predicting Trends

• Three characteristics explain trends
• Shells
• Shielding e-
• Protons

Group
Period
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Examples

• Which atom has the larger radius?

• Be or Ba
• Ca or Br

Ba Ca
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Examples

• Which atom has the higher 1st I.E.?

• N or Bi
• Ba or Rn

N Rn
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Examples

• Which atom has the higher melting/boiling point?

• Li or C
• Cr or Kr

C Cr
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Examples

• Which atom has the higher density?

• Be or C
• Cr or W

C W
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Examples

• Which particle has the larger radius?

• S or S2-
• Al or Al3

S2- Al
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Examples

• Which atom has the larger electronegativity?

• Li or F
• Be or Ra

F Be