Structure and Bonding

• Covalent Bond

  A chemical bond formed when electrons are shared between two atoms.

  Only takes place between non-metal elements
• Small covalent molecules

  low melting and boiling point

  they are usually gases or liquids at room temperature
• the reason why small covalent bonds have low melting and boiling point is because there are weak intermolecular forces between the molecules
• small covalent bond do not conduct electricity
• Giant Covalent Substances

  • Diamond
  • Silicon Dioxide
  • Graphite
• Giant covalent substances all have high melting and boiling point
• Diamond

  • Formed from the element Carbon
  • Extremely hard substance
  • It cannot conduct electricity
• Silicon Dioxide

  • Formed from the element Silicone and Oxygen
• Graphite

  • Formed from the element Carbon
  • soft and slippery
  • Good conductor of electricity because of delocalised electron
• Metals have high melting and boiling point because energy is needed to break the strong metallic bonds
• Metals are good conductors of heat and electricity because the delocalised electron can move
• Metals can be bent and shaped because they are malleable
• Alloys

  An alloy is a mixture of metals

  Alloys are harder than pure metals