Periodic Properties

1
Periodic Properties

• Historical development
• Trends
• Periodicity- to occur at regular intervals

2
Historical Development

• Doberiners Triads- 3 elements grouped together
  w/ smilar properties put in order of increasing
  atomic mass
• Newlands Octaves- placed known elements in order
  of increasing atomic mass every 8th element had
  similar properties

3
Historical Development

• Medeleev- father of the P-table
• Arranged known elements by increasing atomic
  mass left blanks for the yet undiscovered
  elements noted periodicity of properties
• Modern P-table- arranged by increasing atomic
  number based on Moselys x-ray defraction
  studies of the elements

4
Periodic Table

• Groups/Families
• Same of e-s in outer shell valence e-s
• Properties are similar vary systematically
• Periods
• Horizontal rows
• Ea row fills an e- shell
• properties repeat periodically

5
Periodic Table

• Organized by atomic structure
• Increasing atomic
• E- configuration
• Properties are determined by e- configuration
• Groups have similar properties similar valence
  e- configuration!

6
Select Group Characteristics

• Alkali Metals -Group 1 or IA
• Very reactive not found as free elements
• Floats on H2O
• Low melting boiling pts
• Reacts w/ H2O to form H2(g) alkali soln

7
Select Group Characteristics

• Alkali Earth Metals - 2 or IIA
• Denser, harder, higher melting boiling pts than
  grp 1
• Less reactive than grp 1, but still not in
  elemental state
• Halogens (salt makers)- 7 or VIIA
• Colored
• Poisonous
• Diatomic
• Very reactive

8
Select Group Characteristics

• Noble Gases 18 or VIIIA
• Unreactive, inert, stable full valence-gt octet
  rule
• Transition Metals
• Central block
• More complicated e- arrangement
• Form colored comps
• Often used as catalysts
• Representative elements
• Those other than the transition elements

9
Periodic Trends

• Electron Affinity- E change th occurs w/ the
  addition of an e- to a neutral atom
• Most elements release E, so EA values are
  negative
• F(g) e- -gt F-(g) E (-328 kJ/mol)
• Indicates the ease w/ wh an atom gains an e-
• Halogens have the highest e- affinity

10
Periodic Trends

• Oxidation/valence number
• Atomic Radii
• Decrease gt w/ NC (across a period)
• Increase down a group as E levels are added
• Ionic Radii
• ions form when atoms gain/lose e-s to get a full
  valence
• Nonmetals gain e-s form larger ions
• Metals lose e-s form smaller ions

11
Periodic Trends

• Density
• Increases then decreases as we proceed across a
  period
• Ionization Energy
• E required to remove an e-
• increases up the groups towards Noble gases
• Factors that Effect IE
• 1. Nuclear Charge NC IE
• 2. Shielding Effect SE, decreases IE
• 3. Radius R, decreases IE
• metals have low IE
• nonmetals have high IE