covalent bonding

• Covalent bonds are formed by the sharing of electrons between atoms.
• The two types of covalent lattices are; covalent network lattice and covalent layer lattice
• diamond is an example of a covalent network lattice
• graphite is an example of covalent layer lattice
• Covalent network lattices have a three dimensional structure where each atom is bonded to its neighbouring atoms by strong covalent bonds forming continuous network throughout the crystal. The lattice is made up of millions of carbons atoms where each carbon atom is bonded to four other carbon atoms.
• In covalent layer lattices have a two dimensional structure where each atom is bonded to neighbouring atoms in a plane by strong covalent bonds forming a repeated pattern of layers. Each layer of the lattice has carbon atoms strongly bonded to 3 other carbon atoms within same plane.
• melting and boiling points increase as the intermolecular forces increase; hydrogen bonding > dipole-dipole interaction > dispersion forces
• water has all three intermolecular forces
• the three intermolecular forces are; hydrogen bonding, dipole-dipole interactions and dispersion forces
• all molecular compounds have dispersion forces
• polar bonds are attracted to more electronegative atoms, central atom has lone pairs
• non polar bonds result from a bond between same elements
• Non polar bonds occurs between two identical atoms or if electrons are shared equally
• allotropes are same elements with different physical forms
• examples of allotropes are diamond, graphite and charcoal
• Covalent bonds will not conduct electricity unless dissolved in water (polar)
• Diamond and graphite are exceptions to the conductivity rule of covalent bonds
• Higher the bond dissociation energy, stronger the covalent bond
• properties of covalent network lattice; covalent network lattices are hard and rigid due to strong covalent bond
• properties of covalent network lattice; covalent network lattices have high sublimation as large amount of energy is required to overcome strong covalent bonds
• properties of covalent network lattice; covalent network lattices do not conduct electricity because there is no free electrons available to move around
• properties of covalent layer lattice; covalent layer lattice are soft and greasy as they have week dispersion forces allowing layers to slide over one another
• properties of covalent layer lattice; covalent layer lattice conduct electricity as the 4th electron from each carbon atom is delocalised and free to move within layers
• properties of covalent layer lattice; covalent layer lattice have high sublimation points as large amounts of energy is required to distribute strong covalent bonds.
• Hydrogen bonding only occurs when hydrogen is bonded to fluorine, nitrogen or oxygen atoms
• dipole-dipole interaction only occurs in polar bonds
• dispersion forces occurs in all bonds
• shape: tetrahedral

  
• shape: planar

  
• shape: pyramidal

  
• shape: bent or v-shape

  
• shape: trigonal planar

  
• Polar molecules are asymmetrical
• Non polar molecules are symmetrical, have equally distributed non polar or polar bonds
• a double or triple bond is stronger than a single bond
• Does diamond conduct electricity?


  No, as in diamond bonds each carbon is bonded with four other carbon bonds. This means that all electrons are localised in bonding therefore there are no freely moving charged particles to carry electricity.
• Does graphite conduct electricity?

  Yes as in graphite bonds, each carbon atom is covalently bonded to three other carbon atoms, leaving one delocalised electron per carbon. These delocalised electrons can then move freely conducting electricity.