A-level Chemistry: 3.1.3 Bonding Part 1

Electrostatic force of attraction between oppositely charged ions formed by electron transfer

Metal atoms lose electrons to form +ve ions

Non-metal atoms gain electrons to form -ve ions

single atoms which have lost/gained electrons to make full outer shell

Ions that are made up of groups of atoms with an overall charge

SO42-

OH-

NO3-

CO32-

NH4+

Giant Ionic Lattice

NaNO₃

MgCl₂

1. Conduct electricity only when they’re molten or dissolved

2. High melting points

3. Tend to dissolve in water

∵ ions in liquid are free to move and carry a charge

∵ ions are in fixed position by strong ionic bonds

• 
  Giant ionic lattices

• Strong electrostatic forces of attraction between oppositely charged ions

• Takes a lot of energy to overcome these forces

• Water molecules are polar
  

  • Part of molecule has a small negative charge and other bits have small positive charges

• Charged parts pull ions away from lattice = causing it dissolve

smaller and/ or have higher charges

• Form when 2 or more atoms bond together

• Held together by strong covalent bonds

Shared pair of electrons

1. 
   Two atoms share electrons so they’ve both got full outer shells

2. Both postive nuclei are attracted electrostatically to shared electrons

multiple shared pairs of electrons

∵ they can form 4 covalent bonds

• Carbon atoms are arranged in sheets of flat hexagons covalently bonded with 3 bonds each

• 4th outer electron of each carbon atom is delocalised

• Sheets of hexagons are boned together by weak van der Waal forces

1. Low density

2. Dry lubricant/slippy

3. Electrical conductor

4. Insoluble in any solvent

5. Very high melting point

Layers are quite far apart compared to the length of covalent bonds

'Delocalised' electrons aren't attached to any particular carbon atoms & free to move along sheets carrying a charge

Weak bonds between layers in graphite = easily broken ∴ sheets can slide over each other

Covalent bonds are very strong and require lots of energy to break

Covalent bonds in sheets are too strong to break

• Each carbon atom is covalently bonding to 4 other carbon atoms (giant covalent structure)

• Tetrahedral shape

1. Very high melting point

2. Extremely hard

3. Good thermal conductor

4. Can't conduct electricity

5. Won't dissolve in any solvent

Vibrations travel easily through stiff lattice

Outer electrons held in localised bonds

Its structure makes it refract light a lot

When shared pair of electrons in covalent bond come from only one of the bonding atoms

Ammonium ion (NH4+)

Forms when nitrogen atom in ammonia molecule donates a pair electrons to proton (H+)

Metallic bonding is the electrostatic force of attraction between the positive metal ions and the delocalised electrons

giant metallic lattice structures

1. Outer shell electrons of metal are delocalised

   1. Electrons free to move

   2. Leaves positive metal ion

2. Positive metal ions attracted to delocalised negative electrons

   1. Form lattice of closely packed positively ions in sea of delocalised electrons

   2. This is metallic bonding

• High melting points

• Good thermal conductors

• Good electrical conductors

• Insoluble (expect in liquid metals)

Strong electrostatic attraction between positive metal ions and delocalised sea of electrons

Delocalised electrons can pass kinetic energy to each other

Delocalised electrons can move and carry current

Strong metallic bonds

1. Number of protons/strength of nuclear attraction

2. Number of delocalised electrons per atom

3. Size of ion

stronger bond

stronger bonding

stronger the bond

1. In Mg: more electrons in outer shell that are released to sea of electrons

2. Mg ion is smaller and has more than one proton

3. ∴ stronger electrostatic attraction between positive metal ions and delocalised electrons = higher energy is needed to break bonds

The number of pairs of electrons in outer shell of central atom

charge clouds

Area where you have really big chance of finding an electron pair

Electrons = negatively charged ∴ repel each other

how much it repels other charge clouds

e.g. lone-pair charge clouds repel more than bonding-pair charge clouds

∵ they're pushed together by lone-pair repulsion

Lone-pair/lone-pair

Lone-pair/bonding-pair

Bonding-pair/bonding-pair

Linear

Trigonal planar

Tetrahedral