Covalent Bonding

• In covalent bonding the particles are atoms which share pairs of electrons
• Covalent bonding occurs in most non-metallic elements and in compounds of non-metals
• When atoms share pairs of electrons, they form covalent bonds. These bonds between atoms are strong
• A dot and cross diagram can be used to show bonding in covalent compounds 


  The shared electrons are drawn in the overlap

  
• Dot and cross diagrams do not show the relative sizes of the atoms or how they are arranged
• The displayed formula is good for shows the covalent bonds as single lines between atoms
• The displayed formula is good for shows the covalent bonds as single lines between atoms 


  e.g. ammonia

  
• Three dimensional models do not show where the electrons in the bonds have come from 


  They can also get confusing for large molecules that include a lot of atoms

  
• Simple molecular structures have atoms held together by very strong covalent bonds but the intermolecular forces between the molecules are very weak
• The melting and boiling point of simple molecular substances are low because the intermolecular forces are weak
• Simple molecular compounds do not conduct electricity because they do not have any free electrons or ions
• Small molecules substances do not conduct electricity because the molecules do not have an overall electric charge