bonding and structure

• ionic bonding


  the electrostatic attraction between positive and negative ions
• covalent bonding


  electrostatic attraction between a shared pair of electrons and the nuclei
• metallic bonding


  electrostatic attraction between the positive metal ions and the sea of delocalised electrons
• why do giant iconic lattices conduct electricity when liquid but not solid?

  In solid state the ions are in fixed positions and cannot move

  when they are in a liquid state the ions are mobile and can freely carry the charge
• do giant ionic lattices have a high or low melting and boiling point?

  high mating and boiling point because a large amount of energy is required to overcome the electrostatic bonds
• in what type of solvents do lattices dissolve?

  polar solvents e.g. water
• why are ionic compounds soluble in water?

  water has a polar bond. Hydrogen atoms have a + charge and oxygen atoms have a - charge which are able to attract charged ions
• how many covalent bonds does carbon form?

  4
• how many covalent bonds does oxygen form?

  2
• what is a lone pair?

  electrons in the outer shell that are not involved in the bonding
• dative covalent bond


  bond where both of the shared electrons are supplied by one atom
• how are oxonium ions formed?


  formed when acid is added to water
• what does expansion of the octet mean?

  when a bonded atom has more than 8 electrons in the outer shell
• types of covalent structures

  • simple molecular lattice
  • giant covalent lattice
• describe the bonding in simple molecular structures

  atoms within the same molecule are held together by strong covalent bonds and different molecules are held by weak intermolecular forces
• can simple molecular structures conduct electricity?

  no
• why do simple molecular structures not conduct electricity?

  they have no free charged particles to move around
• simple molecular structures dissolve in what type of solvent?

  non polar solvents
• examples of giant covalent structures

  • Diamond
  • Graphite
  • Silicon dioxide
• properties of giant covalent structures

  • high melting and boiling points
  • non conductors of electricity except graphite
  • insoluble in plat and non polar solvents
• how does graphite conduct electricity

  delocalised electrons present between the layers are able to move freely carrying the charge
• describe the structure of a Dimond

  3D tetrahedral structure of c atoms with each c atom bonded to 4 others
• shape and bond angle of a shape with 2 bonded pairs and 0 lone


  180 and linear
• shape and bond angle of a shape with 3 bonding pairs and 0 lone pairs


  trigonal planar and 120
• shape and bond angle of a shape with 4 bonding pairs and 0 lone pairs

  tetrahedral and 109.5
• shape and bond angle of a shape with 5 bonding pairs and no lone pairs


  Trigonal bipyramid and 90 and 120
• shape and bond angle of a shape with 6 bonding pairs and no lone pairs


  octahedral and 90
• shape and bond angle of a shape with 3 bond pairs and 1 Lone pair

  pyramidal and 107
• shape and bond angle of a shape with 2 bond pairs and 2 lone pairs


  non linear and 104.5
• by how many degrees does each lone pair reduce the bond angle?

  2.5 degrees
• electronegativity


  the ability of an atom to attract the pair of electrons in a covalent bond
• in which direction of the periodic table does electronegativity increase?

  top right towards fluorine
• non polar bond


  the electrons in the bond are evenly distributed
• most electronegative element


  fluorine
• how is a polar bond formed?

  bonding atoms have different electronegativities
• why is h20 polar whilst co2 is non polar?

  co2 is a symmetrical molecule so no dipole
• two types of molecular forces

  • hydrogen
  • van der Waals
• two interactions that can be referred to van Der Waals forces

  • permanent dipole-induced dipole interaction
  • permanent dipole-permanent dipole interaction
• describe permanent dipole-induced dipole interactions

  when a molecule with a permanent dipole is close to another non polar molecules it causes the non polar molecule to become slightly polar leading to attraction
• London forces

  • caused by random movements.of electrons
  • leading to instantaneous dipoles
  • they induce a dipole in a nearby molecule
  • induced dipoles attract one another