Covalent

• How atoms can form covalent bonds

  1. Sharing electrons

  2. Drawing covalent bonds
• Ionic bonds

  Atoms transfer electrons from one to the other, forming oppositely charged ions that are attracted through electrostatic forces
• Atoms transfer electrons to get a full outer shell
• This works when one atom has too many electrons and the other too few, like sodium and chlorine
• When two non-metal elements like two chlorine atoms need an extra electron, they can share electrons instead of transferring them
• Dot and cross diagram


  Used to show which electrons belong to each atom when drawing covalent bonds
• Displayed formula

  Writes the chemical symbols of atoms and uses lines to show covalent bonds
• Displayed formulas are easier to draw for large molecules than dot and cross diagrams
• Displayed formulas don't show the 3D shape of the molecule
• Drawing covalent bonding in ammonia (NH3)

  1. Draw all atoms with outermost shells

  2. Determine how atoms can fit together to have full outer shells

  3. Draw dot and cross diagram

  4. Draw displayed formula by replacing shells and electrons with lines
• Simple molecular substances


  Small molecules where atoms are joined by strong covalent bonds, but between molecules there are only weak intermolecular forces
• Polymers


  Long chains made up of repeating monomer units
• Giant covalent structures

  Structures like silicon dioxide, diamond, and graphite with billions/trillions of atoms joined by covalent bonds in a regular lattice