Week 3 - Powerpoint 2

• What is the definition of first ionisation energy?


  The energy required to remove one electron from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1$+$.
• How do first ionisation energies trend across periods 2 and 3?


  They generally increase due to increased nuclear charge and decreased atomic radius.
• How do trends in ionisation energies support the Bohr model of the atom?


  They demonstrate that electrons are held more tightly as nuclear charge increases, consistent with the Bohr model.
• How can you determine the group of an element based on its successive ionisation energies?


  By analyzing the large jumps in ionisation energy, which indicate the removal of core electrons.
• What are the trends of physical and chemical properties across periods 2 & 3 and down groups 2 & 7?


  Physical and chemical properties vary systematically, with changes in reactivity and state of matter.
• What is the definition of disproportionation?


  It is a reaction in which a single substance is both oxidized and reduced.
• What are the main trends in the periodic table regarding atomic radius?


  • Atomic radius increases down a group due to more energy levels.
  • Atomic radius decreases across a period due to increased nuclear charge.
• How is atomic radius generally defined?


  As half the distance between the nuclei of one atom and the nuclei of the neighboring atom.
• What is the trend in ionic radius for cations compared to their parent atoms?


  Cations have a smaller radius than the parent atom due to increased effective nuclear charge.
• What is the trend in ionic radius for anions compared to their parent atoms?


  Anions have a larger radius than the parent atom due to decreased effective nuclear charge and increased electron repulsion.
• What are the factors affecting ionisation energy?


  • Atomic radius: Further electrons are held less tightly.
  • Effective nuclear charge: More protons increase attraction on outer electrons.
  • Electron shielding: More inner shells reduce the effective nuclear charge felt by outer electrons.
• Why does ionisation energy decrease down a group?


  Due to increased distance from the nucleus and increased shielding.
• Why does ionisation energy increase across a period?


  Because the smaller the atom, the stronger the attraction of the nucleus on the outer electrons.
• What causes small jumps in ionisation energy within each group?


  Stable electron configurations (full orbitals) resist losing electrons.
• How can orbital diagrams help explain dips in ionisation energy?


  They show that removing an electron can lead to a more stable configuration with unpaired electrons.
• What is the trend in successive ionisation energies?


  Ionisation energies increase as more electrons are removed due to increased effective nuclear charge.
• What happens when a core electron is removed during ionisation?


  A large jump in ionisation energy occurs due to the increased effective nuclear charge on remaining electrons.
• What is the summary of ionisation energy trends?


  • Ionisation energy increases as atomic/ionic radii decrease.
  • Ionisation energy increases as effective nuclear charge increases.
  • First ionisation energy increases moving up a group and to the right across a period.
• What is the definition of first electron affinity?


  The energy released when 1 mole of gaseous atoms acquire an electron to form 1 mole of gaseous 1$-$ ions.
• How does electron affinity trend across the periodic table?


  Generally, electron affinity increases as atomic radius decreases.
• What factors affect electron affinity?


  Nuclear charge, distance from the nucleus, and shielding affect electron affinity.
• What is the trend in successive electron affinities?


  Adding a second electron requires energy due to repulsion in an already negative ion.
• What are the structures and properties of Period 3 elements?


  • Na, Mg, Al: Metallic structures with increasing valence electrons and stronger metallic bonding.
  • Si: Giant covalent structure with a tetrahedral network.
  • P, S, Cl, Ar: Simple covalent structures with low melting and boiling points.
• What do all elements in period 3 react with oxygen to form?


  Oxides.
• How do the melting and boiling points of Period 3 oxides vary?


  They depend on the number of electrons in the molecule.
• What is the structure of sulfur in Period 3?


  Sulfur exists as S$_8$.
• What is the structure of phosphorus in Period 3?


  Phosphorus exists as P$_4$.
• What is the structure of chlorine in Period 3?


  Chlorine exists as Cl$_2$.
• What is the trend in melting and boiling points for Period 3 elements?


  They generally increase with the number of electrons in the molecule.
• What are the general trends in reactivity for Period 3 elements?


  • Metals tend to lose electrons to form cations.
  • Non-metals tend to gain electrons to form anions.
• What are the main trends in the periodic table regarding ionisation energy?

  • Ionisation energy increases as atomic radius decreases.
  • Ionisation energy increases as effective nuclear charge increases.
  • First ionisation energy increases moving up a group and to the right across a period.
• What is the first electron affinity of oxygen?


  • 142 kJ mol^-1
• What is the second electron affinity of oxygen?


  +844 kJ mol^-1
• What does the difference in sign of the first and second electron affinities indicate?


  The first electron affinity releases energy, while the second requires energy input.
• Why does adding a second electron to an oxygen ion require energy?


  It requires energy because the second electron is forced into an already negative ion, which is unfavorable.
• What are the structures and properties of Period 3 elements from sodium to argon?


  • Na, Mg, Al: Metallic structures with increasing valence electrons leading to stronger metallic bonding.
  • Si: Giant covalent structure with a tetrahedral network of Si-Si bonds.
  • P, S, Cl, Ar: Simple covalent structures with low melting and boiling points due to van der Waals forces.
• What is the general equation for the reaction of elements in Period 3 with oxygen?


  Element + O₂ → oxide
• How do the reactivities of metals in Period 3 with oxygen vary?


  More reactive metals like Na and Mg react readily, while Al and Si react slowly.
• What are the melting points of Period 3 metal oxides and why are they high?


  • High melting points due to giant ionic lattices.
  • Strong ionic bonds require a lot of energy to break.
  • MgO has a higher melting point than Na₂O due to higher charge density on Mg²⁺ ions.
• Why does Al₂O₃ have a lower melting point than expected?


  High charge density of Al³⁺ distorts the electron cloud of oxygen, making bonds partially covalent.