Bonding and structure

• What are the three main types of chemical bonds?

  Ionic, covalent, and metallic
• How is ionic bonding defined?

  It is the electrostatic attraction between positive and negative ions
• Give an example of an ionically bonded substance.

  NaCl (Sodium Chloride - salt)
• How is covalent bonding defined?

  It is the electrostatic attraction between a shared pair of electrons and the nuclei
• How is metallic bonding defined?

  It is the electrostatic attraction between the positive metal ions and the sea of delocalised electrons
• In a dot and cross diagram, which electrons are represented?

  Electrons in the outer shell
• Why do giant ionic lattices conduct electricity when liquid but not when solid?

  In solid state, the ions are in fixed positions and cannot move; in liquid state, the ions are mobile and can carry 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 electrostatic bonds
• In what type of solvents do ionic lattices dissolve?

  Polar solvents, e.g., water
• Why are ionic compounds soluble in water?

  Water has a polar bond, allowing it to interact with ionic compounds
• 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 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?

  It is a measure of average energy needed to break the bond
• What is a dative covalent bond?

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

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

  It means when a bonded atom has more than 8 electrons in the outer shell
• What are the types of covalent structure?

  Simple molecular lattice and giant covalent lattice
• Describe the bonding in simple molecular structures.

  Atoms within the same molecule are held by strong covalent bonds, while different molecules are held by weak intermolecular forces
• Why do simple molecular structures have low melting and boiling points?

  Only a small amount of energy is needed to overcome the intermolecular forces
• Can simple molecular structures conduct electricity?

  No, they are non-conductors
• 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
• Give examples of giant covalent structures.

  Diamond, graphite, and silicon dioxide (SiO2)
• List some properties of giant covalent structures.

  High melting and boiling points, non-conductors of electricity (except graphite), insoluble in polar and non-polar solvents
• How does graphite conduct electricity?

  Delocalised electrons present between the layers can move freely, carrying the charge
• Why do giant covalent structures have high melting and boiling points?

  Strong covalent bonds within the molecules need to be broken, which requires a lot of energy
• Draw and describe the structure of a diamond.

  It has a 3D tetrahedral structure of carbon atoms, with each carbon atom bonded to four others

  
• What does the shape of a molecule depend on?

  It depends on the number of electron pairs in the outer shell and the number of these electrons that are bonded and lone pairs
• What is the shape, diagram, and bond angle in a shape with 2 bonded pairs and 0 lone pairs?

  Linear with a bond angle of 180°
• What is the shape, diagram, and bond angle in a shape with 3 bonding pairs and 0 lone pairs?

  Trigonal planar with a bond angle of 120°
• What is the shape, diagram, and bond angle in a shape with 4 bonded pairs and 0 lone pairs?

  Tetrahedral with a bond angle of 109.5°
• What does the shape of a molecule depend on?

  Number of electron pairs in the outer shell
• What factors determine the shape of a molecule?

  Number of bonded electrons and lone pairs
• What is the shape, diagram, and bond angle in a molecule with 2 bonded pairs and 0 lone pairs?

  Linear, 180°
• What is the shape, diagram, and bond angle in a molecule with 3 bonded pairs and 0 lone pairs?

  Trigonal planar, 120°
• What is the shape, diagram, and bond angle in a molecule with 4 bonded pairs and 0 lone pairs?

  Tetrahedral, 109.5°