Chemical bonding & structure and properties of materials

• Ionic compounds gain or lose electrons to attain noble gas configuration
• Covalent compounds share electrons to attain noble gas configuration
• An ionic bond is formed when a metal reacts with a non-metal
• A covalent bond is formed when a non-metal and a non-metal share electrons
• In ionic compounds, the positive and negative ions are very strongly attracted to one another by strong electrostatic forces, forming a giant crystal lattice structure
• An ionic compound is naturally neutral because they have no net charge

  The sum of positive and negative charges is the same
• Physical properties of ionic compounds:

  • has a high melting point
  • requires a large amount of energy to overcome the strong electrostatic forces of attraction between the positive and negative ions
• Solubility of ionic compounds

  • usually soluble in water, but insoluble in organic solvents
  • water molecules can separate the positive ions from the negative ions, causing them to dissolve
• Electrical conductivity of ionic compounds

  • non-conductors of electricity in the solid state but conduct electricity when in molten or aqueous state
  • ions in solid state are held together in fixed positions - ions are not free to move and cannot conduct electricity
  • when molten or aqueous, ions are mobile and can carry current to conduct electricity
• Physical properties of covalent compounds

  covalent compounds exist either as simple molecular structures or giant molecular structures

  
  

  most covalent structures have simple molecular structures
• Melting and boiling points of covalent compounds

  • low melting or boiling point
  • little amount of energy needed to overcome the weak intermolecular forces of attraction
• solubility of covalent substances

  usually insoluble in water, but soluble in organic solvents
• electrical conductivity for covalent substances

  • non-conductors of electricity in any state
  • substances with simple molecular structures have no mobile ions or mobile electrons to carry electric current