Bonding, Structure and Properties of Matter

• Ionic bonding happens between a metal and a non-metal
• Ions - charged particles that form when an atom loses or gains an electron when they're trying to get a full outer shell to become stable
• When metals and non-metals react together, the metal atom loses electrons to form a positively charged ion and the non-metal atom gains these electrons to form a negatively charged ion. These ions are strongly attached to each other by electrostatic forces, called an ionic bond
• Ionic bonding - sodium chloride NaCl - Sodium loses an electron. Chlorine gains an electron. They both have full outer shells. They're held together by electrostatic forces.

  A) Na+

  B) Cl-

  
• Ionic bonding - Calcium fluoride CaF2 - Calcium needs to lose 2 electrons to become stable but fluorine only needs to gain 1 electron so for the reaction to happen there needs to be 2 fluorine atoms.

  A) 2

  B) 2+

  C) -

  
• Ionic compounds are any compound that only contain ionic bonds.
• The structure of an ionic compound is called a giant ionic lattice. The ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between oppositely charged ions in all directions in the lattice. A single crystal of sodium chloride would be one giant ionic lattice.

  
• Covalent bonds - non-metal atoms bond together by the sharing of electrons
• Covalent bonds - The positively charged nuclei of the bonded atoms are attracted to the shared electrons by electrostatic forces, making covalent bonds very strong. Atoms can only share electrons in their outer shells. Happens in non-metal compounds (H20) and non-metal elements (Cl2)
• Simple molecular substances are made of a few atoms joined by covalent bonding
• Hydrogen - Only needs one electron to complete its outer shell so only forms a single covalent bond.

  
• Chlorine - Shares one pair of electrons and form a single covalent bond

  
• Oxygen - Two oxygen atoms share two pairs of electrons with each other making a double covalent bond

  
• Nitrogen - Two nitrogen electrons share 3 pairs of electrons making a triple covalent bond

  
• Hydrogen Chloride - Both atoms only need one electron to create a full outer shell so share 1 pair of electrons making a single covalent bond

  
• Methane - Carbon has 4 outer electrons so can form 4 covalent bonds with hydrogen atoms

  
• Water - Oxygen shares a pair of electrons with two hydrogen to form two single covalent bonds

  
• Ionic compounds: Properties - High melting + boiling points as they have strong bonds which take a lot of energy to overcome
• Ionic compounds: Properties - When solid the ions are held in place so can't conduct electricity but when melted the ions are free to move so can conduct electricity (when molten can conduct electricity)
• Ionic compounds: Properties - Dissolve in water easily
• Covalent bonding: Properties of simple molecular substances - Atoms within the molecules are held together by very strong covalent bonds but the forces of attraction between the molecules are very weak. This means the melting and boiling points are very low as the molecules are easily parted from each other due to their feeble intermolecular forces. Most are gases or liquids at room temperature as a result.
• Covalent bonding: Properties of simple molecular substances - Don't conduct electricity as they aren't charged so there are no free electrons or ions.
• Polymers - Lots of small units linked together to form a long molecule that has repeating sections. All the atoms are joined together by strong covalent bonds.
• Polymers: Repeating units

  A) repeating units

  B) large number

  C) n

  D) join up

  E) brackets

  F) shortest

  
• Polymers: Properties - Most are solid at room temperature as the intermolecular forces are stronger. Polymer molecules are larger than between simple covalent molecules. Intermolecular forces are weaker than in ionic or covalent bond.
• Giant covalent structures - All atoms bonded by strong covalent bonds. Very high melting + boiling points as lots of energy is needed to break the covalent bonds between atoms. Don't contain charged particles so don't conduct electricity (except graphite when molten)
• Giant covalent structures - Diamond

  
• Giant covalent structures - Silicon dioxide

  
• Giant covalent structures - Graphite

  
• Allotropes - Different structural forms of the same element in the same physical state.
• Allotropes of carbon: Diamond - Each carbon has 4 covalent bonds - strong + high melting points - don't conduct electricity because there are no free electrons of ions

  
• Allotropes of carbon: Graphite - Each carbon atom forms 3 covalent bonds, creating sheets of carbon in hexagons. There are no covalent bonds between layers (they're only held together weakly) so free to slide over each other - soft + slippery, ideal as lubricants. High melting points as they have strong covalent bonds in the layers. Only 3 out of 4 carbon outer shell electrons are used so each atom has one delocalised electron - can conduct electricity and heat

  
• Allotropes of carbon: Graphene - One sheet of graphite. The layer is one atom thick, making it a two-dimensional compound. The network of covalent bonds makes it very strong + light so can be added to composite materials to improve their strength without adding too much weight. Can conduct electricity.
• Allotropes of carbon: Fullerenes - Molecules of carbon shaped like closed tubes or hollow balls

  
• Allotropes of carbon: Fullerenes - Can form around another atom or molecule which is trapped inside - could be used to deliver a drug.
• Allotropes of carbon: Fullerenes - Have a huge surface area so could make industrial catalyst where the catalyst molecules attach to the fullerenes.
• Allotropes of carbon: Fullerenes - Lubricants
• Allotropes of carbon: Fullerenes, nanotubes - Tiny carbon cylinders, ratio between length + diameter very high, conduct heat + electricity, high tensile strength. Nanotechnology can be used to strengthen materials or be used in electronics without adding too much weight.
• Metallic bonding - metal atoms + metal atoms
• Metallic bonding: properties - Electrostatic forces between the metal atoms and sea of delocalised electrons are very strong so there needs to be lots of energy to break the forces, so metallic compounds have high melting + boiling points and are solid at room temperature.