(g) Covalent Bonding

• Covalent bonding is the electrostatic forces of attraction between two nuclei and a shared pair of electrons
• Simple molecular structures are usually liquids or gases at rtp because they have strong covalent bonds but weak intermolecular forces between individual molecules which require little energy to be overcome
• As the molecule increases in size, the melting and boiling points increase. This is because they have stronger intermolecular forces between molecules so more energy is needed to break them apart
• Simple molecular compounds do not conduct electricity because they have no free electrons or ions to move and carry a charge. This is why they are often used as insulators
• Allotropes are different forms of compounds made from the same element
• • Diamond has strong covalent bonds throughout its structure
  • Each carbon atom is bonded to four other carbon atoms
  • It is hard, has a high boiling point and doesn’t conduct electricity
  • It is used in jewellery, drilling and cutting edges in scalpels

  
• • In graphite, each carbon atom is bonded by strong covalent bonds to three other carbon atoms so one electron is delocalised
  • The structure is arranged into layers which have weak intermolecular forces between individual layers
  • It conducts electricity, has a high melting point and is soft and slippery
  • It is used as electrodes in electrolysis and pencils