6: shapes of molecules and intermolecular forces

• What are the 3 main types of chemical bonds 


  Ionic

  Covalent

  Metallic
• define ionic bonding 


  the strong electrostatic force of attraction between oppositely charged ions
• give examples of an ironically bonded substance 


  NaCl (Sodium Chloride - salt)
• define covalent bonding 


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


  electrostatic attraction between the positive metal ions and the sea of delocalised electrons
• electrons in which shell are represented in a dot and cross diagram 


  the outer shell
• why does giant ionic lattices conduct electricity when liquid but not when solid?


  in a solid state the ions are in fixed positions and thus cannot move. When they are in liquid state the ions are mobile and thus can freely carry the charge
• do giant ionic lattices have high or low melting and boiling points? explain your answer 


  they have high melting and boiling points because a large amount of energy is required to overcome the strong electrostatic forces of attraction between oppositely charged ions
• in what type of solvents do ionic lattices dissolve?


  polar solvents (eg water)
• why are ionic compounds soluble in water?


  water has a polar bond. hydrogen atoms have a S+ charge and oxygen atoms have a S- charge. these charges are able to attract charged ions.
• what is it called when atoms are bonded by a single pair of shared electrons?

  Single bond
• 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
• what is formed when atoms share two pairs of electrons?

  double bond
• What is formed when atoms share three pairs of electrons?

  Triple bond
• what is average bond enthalpy?


  measure of average energy needed to break the bond

  how strong the covalent bond is
• what is a dative colavent bond?

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

  formed when acid is added to water, H3O+
• What does expansion of the octet mean?


  When a bonded atom has more than 8 electrons in the outer shell
• what are the types of covalent structure?


  simple molecular lattice

  giant covalent lattice