PHYSCI

• Chemical Bond


  Bond results from the attraction of nuclei for electrons
• Chemical Bond


  • All atoms trying to achieve a stable octet
• Electronegativity


  The p+ in one nucleus are attracted to the e- of another atom
• Major Types of Bonding

  • Ionic Bonding
  • Covalent Bonding
• Ionic Bonding


  • Forms ionic compounds
  • Transfer of e-
• Covalent Bonding


  • Forms molecules
  • Sharing of e-
• Ionic Bonding (ionic compounds)


  • Electrons are transferred between valence shells of atoms
  • Made of ions
  • Called Salts or Crystals
  • Always formed between metals and non-metals
  • Electronegativity difference: > 2.0
  • Compounds with polyatomic ions
• Covalent Bonding


  • Pairs of e- are shared between non-metal atoms
  • Electronegativity difference: < 2.0
  • Forms polyatomic ions
• Properties of Ionic Compounds/Bonding

  • Hard solid @ 22°C
  • High mp temperatures
  • Non conductors of electricity in solid phase
  • Good conductors in liquid phase or dissolved in water (aq)
• Properties of Molecular Substances (Covalent Bonding)

  • Relatively soft solids as compared to ionic compounds
  • Low m.p. and b.p. temps
  • Non conductors of electricity in any phase
• Metallic Bonding


  • Occurs between like atoms of a metal in the free state
  • Valence e- are mobile (move freely among all metal atoms)
  • Positive ions in a sea of electrons
• Metallic Characteristics

  • High mp temps, ductile, malleable, shiny
  • Hard substances
  • Good conductors of heat and electricity as (s) and (l)
  • Mobile electrons enable metals to conduct electricity
• Types of Covalent Bonds

  • Non-Polar Bond
  • Polar Bond
• Non-Polar Bond


  • Electrons shared evenly in the bond
  • E-neg difference is zero
  • Between identical atoms (Diatomic Molecules)
• Polar Bond


  • Electrons unevenly shared
  • E-neg difference greater than zero but less than 2.0 (closer to 2.0 more polar, more "ionic character")
• Non-Polar Molecules


  Bonds within a molecule are polar but the molecule is non-polar because its shape is symmetrical
• Polar Molecules (Dipoles)


  • Not equal on all sides
  • Polar bond between 2 atoms makes a polar molecule
  • Asymmetrical shape of molecule
• Cl H

  • Space filling model
  • Electron-Cloud model