Ionic and Covalent Bonding

• Ions


  Atoms that have lost or gained electrons to achieve a full outer shell of electrons (like the noble gases)
• Formation of Ions


  1. Loss of electrons: Forms positive ions (cations)

  2. Gain of electrons: Forms negative ions (anions)
• Group Charges


  • Metals in Groups 1, 2, and 3:
  • Group 1: +1 (e.g., Na⁺)
  • Group 2: +2 (e.g., Ca²⁺)
  • Group 3: +3 (e.g., Al³⁺)
  • Non-metals in Groups 5, 6, and 7:
  • Group 5: -3 (e.g., N³⁻)
  • Group 6: -2 (e.g., O²⁻)
  • Group 7: -1 (e.g., Cl⁻)
• Common Transition Metals and Polyatomic Ions

  • Ag⁺ (silver)
  • Cu²⁺ (copper(II))
  • Fe²⁺ (iron(II))
  • Fe³⁺ (iron(III))
  • Pb²⁺ (lead(II))
  • Zn²⁺ (zinc)
  • H⁺ (hydrogen)
  • OH⁻ (hydroxide)
  • NH₄⁺ (ammonium)
  • CO₃²⁻ (carbonate)
  • NO₃⁻ (nitrate)
  • SO₄²⁻ (sulfate)
• Writing Formulae for Compounds

  Combining Ions: To write the formula of an ionic compound, combine the ions in such a way that the total positive charge equals the total negative charge
• Ionic Compound Formulae


  • Sodium chloride (Na⁺ and Cl⁻) forms NaCl
  • Calcium nitrate (Ca²⁺ and NO₃⁻) forms Ca(NO₃)₂
• Dot-and-Cross Diagrams


  • Show the transfer of electrons from one atom to another
  • Only the outer electrons are shown
• Dot-and-Cross Diagrams for Ionic Compounds

  • For NaCl, show Na losing an electron (dot) and Cl gaining an electron (cross)
• Ionic Bonding


  • Ionic bonds are strong electrostatic attractions between oppositely charged ions
  • Giant ionic lattices have high melting and boiling points due to the strong electrostatic forces between ions
  • Ionic compounds conduct electricity when molten or dissolved in water because the ions are free to move
  • Ionic compounds do not conduct electricity when solid because the ions are fixed in place
• Covalent Bonds


  • Formed by the sharing of electron pairs between atoms
  • Usually occurs between non-metal atoms
  • The shared electrons are attracted to the nuclei of both atoms, holding them together
• Dot-and-Cross Diagrams for Covalent Bonds

  • Represent shared electrons with dots and crosses
  • Only the outer electrons are shown
• Dot-and-Cross Diagrams for Covalent Molecules

  • Diatomic Molecules: Hydrogen (H₂), Oxygen (O₂), Nitrogen (N₂), Halogens (e.g., Cl₂), Hydrogen halides (e.g., HCl)
  • Inorganic Molecules: Water (H₂O), Ammonia (NH₃), Carbon dioxide (CO₂)
  • Organic Molecules: Methane (CH₄), Ethane (C₂H₆), Ethene (C₂H₄)