Covalent Molecular/ Network & Ionic Lattice Formulae

• Covalent molecular substance


  A substance where atoms are bonded together by covalent bonds
• Determining the number of atoms in a covalent molecular substance

  1. Look at the chemical formula

  2. Count the number of each type of atom
• Nitrogen hydride


  • Chemical formula NHs
  • Contains 1 nitrogen atom and 3 hydrogen atoms
• Writing the chemical formula for a molecule

  1. Start with C then H

  2. Write the number of each atom
• Chemical formula for the molecule H-C-H

  • CH2
• Covalent network


  Millions of atoms bonded together in a network
• Ionic lattice


  Millions of ions bonded together in a lattice structure
• Chemical formula for covalent network and ionic compounds

  Gives the simplest ratio of atoms/ions in the substance
• Silicon dioxide


  • Chemical formula SiO2
  • For every 1 silicon atom there are 2 oxygen atoms
• Sodium chloride


  • Chemical formula NaCl
  • One sodium ion for every chloride ion
• Covalent networks and ionic lattices

  • High melting point and boiling point
  • Ions not free to move in a solid