Bonding and Structure

• Atoms can form chemical bond(s) to other atom(s) in order to achieve a stable electron configuration.
• Metallic bonding - each atom loses on or more electrons, the electrons are delocalised between a lattice of cations. Metallic bonding is the electrostatic attraction between a lattice of positive metal ions and delocalised electrons.
• Ionic bonding - electron(s) are transferred between atoms, forming anions and cations. Ionic bonding is the electrostatic attraction between oppositely charged ions in a giant ionic lattice.
• Covalent bonding - sharing a pair of electrons (generally non-metal and metal atoms).
• What is the main difference between metallic bonding and ionic bonding?


  In metallic bonding, electrons are lost. In ionic bonding, electrons are transferred. Ionic bonding is between metals ad non-metals, whereas metallic bonding is between one type of metal atom.
• What is the major similarity between ionic and metallic bonding?

  Both have an electrostatic attraction between opposite charges held together by strong electrostatic charges.
• Metals have a high melting and boiling point as a lot of energy is required to overcome the strong electrostatic forces of attraction between positive ion and the 'sea' of delocalised electrons.
• Metals do not dissolve. There is some interaction between polar solvents and charges in the metallic lattice but these lead to reactions, rather than dissolving, e.g. sodium and water.
• Metals can conduct electricity in both solid and liquid states. This is due to the delocalised electrons which are free to move/carry charge around the structure.
• In metals, the metallic bonding is stronger than the attraction of the polar water molecules.
• How does the metallic structure allow metals to be ductile and malleable?


  Because the electrons can move within the structure it has an amount to 'give', which allows the layers to slide past each other. The bonds will not break because they are non-directional.
• Predict which metal out of Na, Mg, and Al will have the highest boiling point and explain your answer.

  Al will have the highest boiling point because the electrostatic forces of attraction are stronger and therefore require more energy to overcome and break.
• Describe the bonding in metals.

  Electrostatic attraction between lattice of fixed metal cations and negative delocalised electrons.
• Why are metals very good conductors of heat?


  Delocalised electrons can move throughout the structure, transferring thermal energy.
• Solubility requires:

  • ionic lattice must be broken down
  • water molecules must attract and surround the ions
• In a compound made of ions with large charges, the ionic attraction may be too strong for water to be able to break down the lattice structure - the compound will then not be very soluble.
• Ionic bonding involves the transfer of electrons from a metallic element to a non-metallic element.
• Metals lose electrons from their valence shell forming positively charged cations.
• When an atom gains electrons it will become negative.
• Negatively charged ions are called anions.
• Cations and anions are oppositely charged and are therefore attracted to each other. Electrostatic attractions are formed between the oppositely charged ions to form ionic compounds.
• Ionic compounds have high melting points as the electrostatic forces of attraction between the oppositely charged ions are strong and requires a lot of energy to overcome and break.
• Dot-and-cross diagrams can be used to illustrate the bonding in ionic compounds where 'dots' are used to represent the electrons from one type of ion and 'crosses' are used to represent the electrons from a different type of ion.
• Explain why the melting point of magnesium oxide, MgO, is much higher than that of those in sodium chloride, NaCl.


  Magnesium ions have a greater charge than sodium ions.

  Oxide ions have a greater charge than chloride ions.

  The electrostatic attraction between oppositely charged ions is much greater in MgO than it is in NaCl.

  The ionic bonding is much stronger in MgO than it is in NaCl.
• What type of structure is exhibited in both NaOH and MgCO3?

  Giant ionic lattices.
• Bonding can be ionic, covalent, or metallic.
• Structure can be giant (strong bonds holding the structure together) or simple (weak intermolecular forces between molecules).
• Most ionic, metallic, and covalent solids are crystalline lattices. The ions, atoms, or molecules are arranged in a regular and repeating arrangement.
• When an ionic compound is formed, the attraction between the ions happens in all directions.
• Ionic compounds are arranged in giant ionic lattices (also called giant ionic structures).
• Most ionic compounds are solids at room temperature - there isn't enough energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions that make up the lattice.
• High temperatures are required to make an ionic compound melt or boil.
• Melting and boiling points are also higher for ionic lattices that contain ions with a greater ionic charge.

  For example, the melting point of sodium oxide is 1405K while the melting point of calcium oxide is 2845K. This is due to a stronger attraction between the ions.
• Many ionic compounds will dissolve in polar solvents, e.g. water.
• Polar molecules, such as water, can break down or disrupt the ionic lattice and surround each ion in solution.
• The solubility of an ionic compound depends on the relative strength of the electrostatic forces of attraction within the ionic lattice and the attractions between the ions and the polar molecule.
• Ionic compounds do not conduct electricity when solid.

  This is because the ions are in fixed positions within the solid lattice so there are no mobile charge carriers.
• Ionic compounds can conduct electricity when they are molten or aqueous.

  This is because the ions are no longer in fixed positions as the lattice has broken down, therefore, the ions are free to act as mobile charge carriers.
• What type of structure does sodium chloride have?

  Giant ionic lattice.
• Would you expect sodium chloride to have a high or low melting point?

  High - lots of energy required to break the strong electrostatic forces between oppositely charged ions.