1.3 bonding

• Explain the energy change associated with melting

  Energy is supplied to the solid particles causing them to vibrate faster, weakening the forces between the particles.
• Explain the energy change associated with evaporation

  Energy is supplied to the liquid particles causing them to vibrate faster, completely removing the forces between the particles.
• Explain the energy change associated with freezing

  Energy is given out and the liquid particles move more slowly until they vibrate about a fixed point, the forces between the particles are moved
• Explain the energy change associated with condensation

  Energy is given out and the gaseous particles move much more slowly, the forces between the particles are reformed, so the particles are much closer together
• Explain the energy change associated with sublimation

  Energy is supplied to the solid particles causing them to vibrate faster, if the intermolecular forces are weak, little energy is required to overcome them
• What are the four structures of crystal?

  Giant ionic crystal, Simple molecular, Giant covalent and Giant metallic
• What is the charge of ammonium?

  NH₄ has a charge of +1
• What is the charge of a hydroxide ion?

  OH has a charge of -1
• What is the charge of a sulphate ion?

  SO₄ has a charge of -2
• What is the charge of a nitrate ion?

  NO₃ has a charge of -1
• What is the charge of a carbonate ion?

  CO₃ has a charge of -2
• What is the charge of a hydrogen sulphate ion?

  HSO₄ has a charge of -1
• What is the definition of an ionic bond?

  The electrostatic attraction between oppositely charged ions
• Explain how Na⁺ is formed using a equation in your answer.

  Na --> Na⁺ + e⁻

  Sodium atom loses an electron
• Explain why ionic substances have high melting points.

  X has a giant ionic structure. A large amount of energy is required to break the strong electrostatic attraction between the positive and negative ions
• Explain why ionic substances do not conduct electricity when solid.

  X has a giant ionic structure. The ions are fixed in the lattice and cannot move to carry charge.
• Explain why ionic substances conduct electricity when molten or in an aq solution.

  X has a giant ionic structure. The ions are free to move, so they can carry charge in one direction.
• Explain why ionic substances dissolve well in polar solvents (e.g. water).

  X has a giant ionic structure. Polar solvent molecules attract ions out of the lattice into solution.
• Explain why ionic substances are brittle.

  X has a giant ionic structure. The layers in the ionic lattice cannot easily slide over each other. If the layers of ions do slide over each other, ions of the same charge repel each other and the structure breaks down.

  
• What is the definition of metallic bonding?

  Electrostatic force of attraction between positive metal ions and delocalised electrons.
• Why does calcium have stronger bonding than potassium?

  The calcium ion is smaller and has a higher charge than a potassium ion. The electrostatic force of attraction between a calcium ion and the delocalised electrons is greater.
• Explain why metallic substances have high melting points.

  X has a metallic structure. A large amount of energy is required to break the strong electrostatic attraction between the positive ions and the delocalised electrons.
• Explain why metals conduct electrisity well when sold or molten.

  X has a metallic structure. The delocalised electrons are free to move between metal ions, so they can carry charge in one direction.
• Explain why metallic substances are malleable and ductile / easy to work.

  X has a metallic structure. The layers of ions in the metallic lattice can slide over each other. As the layers of ions slide the electrostatic attraction between the positive ions and the delocalised electrons does not change.
• Describe the bonding in potassium

  Potassium has a giant metallic structure. There is a strong electrostatic force of attraction between positive metal ions and delocalised electrons.
• What is the definition of covalent bonding?

  A bond formed by a shared pair of electrons
• Explain why giant covalent structures have very high melting points.

  X has a giant covalent structure. A large amount of energy is required to break the strong covalent bonds between all the atoms.
• Explain why giant covalent structures are extremely hard

  X has a giant covalent structure. All the atoms are joined by strong covalent bonds which required lots of energy to break.
• Explain why giant covalent structures do not conduct electrisity.

  X has a giant covalent structure. The electrons are fixed in the covalent bonds and are not free to move.
• Explain why graphite has a high melting point.

  Graphite has a giant covalent structure. A large amount of energy is required to break the strong covalent bonds between the atoms in the layers of carbon atoms.
• Explain why graphite is soft

  The weak Van Der Waal's intermolecular forces between the layers of carbon atoms allow the layers to slide over each other.
• Explain why graphite conducts electricity

  Graphite has a giant covalent structure, with delocalised electrons between the layers of carbon atoms. The delocalised electrons are free to move between the layers of carbon atoms, so they can carry charge in one direction.
• Explain why simple molecular structures have low melting points

  Molecules are held together in a simple molecular crystal by weak van der Waals' intermolecular forces, so a small amount of energy is needed to overcome these forces
• Explain why simple molecular structures do not conduct electricity

  There are no free ions or electrons; electrons are fixed in the atom so cannot move and carry charge
• What is dative covalent bonding?

  A bond formed by a shared pair of electrons where both electrons come from one atom
• What does electronegativity mean?

  The ability of an atom to attract the electron pair in a covalent bond
• What is the difference between a pure covalent bond and a polar covalent bond?

  Pure: Two atoms are of the same type and the electron density is shared symmetrically between the two atoms.

  Polar: One atom will attract the pair of electrons more than the other.

  
• Which species contains bonds that have different polarities? NH₄⁺ CCl₄ CH₃Cl H₃O⁺

  CH₃Cl
• What shape of molecules has 2 pairs and what are the bond angles?

  Linear and 180°

  
• What shape of molecules has 3 pairs and what are the bond angles? °

  Trigonal planar, 120°