bonding and structure

• A model showing how metallic bonds are formed - the first diagram shows the outer electrons in their atoms, and the second diagram shows that the electrons have become delocalised

  
• The structure and bonding of metals explains their properties:

  • they are electrical conductors because their delocalised electrons carry electrical charge through the metal
  • they are good conductors of thermal energy because their delocalised electrons transfer energy
  • they have high melting points and boiling points, because the metallic bonding in the giant structure of a metal is very strong - large amounts of energy are needed to overcome the metallic bonds in melting and boiling
• An alloy is a mixture of two or more elements, where at least one element is a metal. Many alloys are mixtures of two or more metals.
• the sodium atom will lose 1 electron it will become a +1 positive ion

  
• negative ions are called anions
• positive ions are called cations
• ions are when electrons are transferred, when atoms lose or gain electrons
• non-metal + non-metal = covalent bonding
• metal +metal = metallic bonding
• metal + non-metal = ionic bonding
• loosing electrons make the atom a positive ion
• gaining electrons make the atom a negative ion
• ionic bonds are strong because they have high melting and boiling points
• Ionic bonding: sodium(metal) will become a positive ion while chlorine(non-metal) will become a negative ion

  
• A molecule is a group of atoms covalently bonded together
• Simple Covalent molecule properties :

  1. Low melting point
  2. Low boiling point
  3. Doesn't conduct electricity
  4. Low density
• Simple covalent molecules do not conduct electricity :

  1. there is no charge
  2. electricity needs charge
• What are the properties of metals?

  Malleable - can be hammered without breaking

  Magnetic

  Lustrous - shiny when polished

  Conductors

  High boiling and melting points

  Ductile - can be drawn into a thin wire
• sea of electrons = delocalised
• in covalent bonding between two non metals they will share electrons so both shells will be full

  
• Intermolecular forces = a weak force of attraction between the molecules