Chapter 7

• How are elements classified in the periodic table?


  Elements are classified as s, p, or d block according to which orbitals the highest energy electrons are in.
• What happens to atomic radii as you move from left to right across a period?

  Atomic radii decrease as you move from left to right across a period.
• Why do atomic radii decrease across a period?

  Because the increased number of protons creates more positive charge attraction for electrons in the same shell with similar shielding.
• What is periodicity in the context of the periodic table?

  • Periodicity is a repeating pattern across different periods.
  • Various properties such as atomic radius, melting points, boiling points, and ionisation energy display periodicity.

  
• How are elements arranged in the periodic table?

  Elements are arranged in increasing atomic number in the periodic table.
• What do elements in the same group have in common?

  Elements in Groups have similar physical and chemical properties due to similar outer shell electron configurations.
• What is the significance of the first ionisation energy graph for periods two and three?

  • The shape of the graph for periods two and three is similar.
  • A repeating pattern across a period is called periodicity.
  • The pattern in the first ionisation energy provides useful information about electronic structure.

  
• What is the definition of first ionisation energy?


  The first ionisation energy is the energy needed to remove an electron from each atom in one mole of gaseous atoms.
• Why does Helium have the largest first ionisation energy?

  Helium has the largest first ionisation energy because its first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells.
• Why do first ionisation energies decrease down a group?

  First ionisation energies decrease down a group because outer electrons are found in shells further from the nucleus and are more shielded, reducing the attraction of the nucleus.

  
• What is the trend in first ionisation energy across a period?

  There is a general increase in first ionisation energy across a period due to increasing proton number while electrons are added to the same shell.
• Why does sodium have a much lower first ionisation energy than neon?

  Sodium has a much lower first ionisation energy than neon because its outer electron is in a 3s shell further from the nucleus and is more shielded.
• Why is there a small drop in first ionisation energy from magnesium to aluminium?

  There is a small drop from magnesium to aluminium because aluminium starts to fill a 3p subshell, which is slightly easier to remove than the 3s electrons in magnesium.

  
• Why is there a small drop in first ionisation energy from phosphorus to sulphur?

  There is a small drop from phosphorus to sulphur because the fourth electron in sulphur starts to doubly fill the first 3p orbital, causing slight repulsion and making it easier to remove.

  
• What is the definition of metallic bonding?


  Metallic bonding is the electrostatic force of attraction between the positive metal ions and the delocalised electrons.
• What are the three main factors that affect the strength of metallic bonding?

  1. Number of protons/strength of nuclear attraction.
  2. Number of delocalised electrons per atom.
  3. Size of ion.
• Why does magnesium have stronger metallic bonding than sodium?

  Magnesium has stronger metallic bonding than sodium because it has more electrons in the outer shell that are released to the sea of electrons and a smaller ion size.
• What are the properties of macromolecular structures?

  • High melting and boiling points due to many strong covalent bonds.
  • Insoluble in water.
  • Poor conductivity when solid (except graphite).
• What are the properties of giant metallic structures?

  • High melting and boiling points due to strong electrostatic forces.
  • Insoluble in water.
  • Good conductivity when solid and molten due to delocalised electrons.

  
• Why does silicon have a very high melting point?

  Silicon has a very high melting point because it is macromolecular with many strong covalent bonds between atoms.
• Why do simple molecular substances have low melting and boiling points?

  Simple molecular substances have low melting and boiling points because of weak London forces between molecules.
• Why does sulfur have a higher melting point than phosphorus?

  Sulfur has a higher melting point than phosphorus because it has more electrons, resulting in stronger London forces.
• What is the trend in melting and boiling points in period 2?

  The trend in melting and boiling points in period 2 shows that lithium and beryllium have high melting points due to metallic bonding, while boron and carbon are macromolecular with very high melting points.

  
• What type of bonding is present in diamond?

  Diamond has covalent bonding with a tetrahedral arrangement of carbon atoms.
• What is the structure of graphite?

  Graphite has a planar arrangement of carbon atoms in layers with delocalised electrons between layers.
• Why are metals malleable?

  Metals are malleable because the positive ions in the lattice can slide easily over one another due to identical attractive forces.
• What are the general properties of macromolecular and giant metallic structures?

  • Macromolecular: high melting and boiling points, insoluble, poor conductivity when solid.
  • Giant metallic: high melting and boiling points, good conductivity when solid and molten, malleable.

  
• What is the trend in melting and boiling points for sodium, magnesium, and aluminum?

  Sodium, magnesium, and aluminum have high melting and boiling points due to strong metallic bonding.
• Why do Cl2, S8, and P4 have low melting and boiling points?

  Cl2, S8, and P4 have low melting and boiling points because of weak London forces between molecules.
• What type of forces exist in argon and what is their effect on its melting point?

  Argon has weak London forces between atoms, resulting in a very low melting point.
• What is the general trend in melting and boiling points across periods in the periodic table?

  • Generally increases for metals due to stronger bonding.
  • Peaks for macromolecular structures.
  • Decreases for simple molecular substances.