Chapter 7 PERIODICITY

• What is Ionisation Energy?

  The minimum energy required to remove one mole of electrons from one mole of atoms in the gaseous state
• How does electron shielding affect ionsiation energy?

  More electron shells between positive nucleus and negative electron being removed so less energy required to remove it due to weaker attraction to nucleus.
• What type of reaction is ionisation energy always?

  Endothermic reaction
• How does atomic size/radius affect ionisation energy?

  The bigger the atom, the further away the outer electrons are from positive nucleus and the attractive force between nucleus & outer electron reduces so less energy required, thus easier to remove
• How does nuclear charge affect ionisation energy?

  More protons in nucleus means greater attraction between nucleus & outer electrons so more energy required to remove the electrons
• What is the trend in ionisation energy down a group and why?

  Ionisation energy decreases down group because atomic radius increases so outer electrons further away & attractive force weakens so energy to remove electrons decreases. Shielding also increases so attractive force weakens and energy to remove decreases
• What is the general trend in ionisation energy across a period and why?

  Ionisation energy increases overall because more protons in nucleus which increases nuclear attraction so more energy required to remove. Shielding is similar and atomic radius decreases marginally meaning more energy required to remove
• Using Period 3 as an example, why is there a decrease in ionisation energy in Aluminium?

  Outer most electron in aluminium sits in a higher energy sub-shell (3p1), slightly further away from nucleus than the outer electron in magnesium (3s2) so less energy is required to remove
• Using Period 3 as an example, why is Sulphur's ionisation energy equivalent to Phosphorous'?

  Phosphorous and sulphur both have outer electrons in 3p orbital so the shielding is the same, however removing an electron from sulphur takes it from an orbital with 2 electrons in. Electron repulsion theory means less energy is needed to remove this electron
• What is successive ionisation energy?

  The removal of more than one electron from the same atom.
• What is the trend in ionisation energies for an atom?

  A general increase in energy as electrons are being removed from an increasingly more positive ion
• Why are there jumps in successive ionisation energy for an atom?

  Jumps because electrons are being removed from orbitals closer to the nucleus
• Using Magnesium as an example, why do the last 2 electrons require the most energy to be removed?

  These electrons are closer to the nucleus than any anothers - in 1s2 orbital
• Why can Graphite conduct electricity?

  Each carbon is bonded 3 times so the 4th electron is delocalised and can carry a charge
• Why can the layers of Graphite slide easily?

  There are weak forces between layers
• Is Graphite soluble?

  No it is insoluble due to strong covalent bonds
• Why does Graphite have a low density?

  The layers are far apart compared to the length of covalent bonds
• Is the melting point of Graphite high or low and why?

  High due to strong covalent bonds which cannot be broken easily
• What are the properties of Graphene which make it useful?

  Lightweight, transparent & good electrical conductor
• What are some of the uses of Graphene?

  Aircraft shells & smartphone screens
• Why is Graphene strong?

  The delocalised electrons strengthen the covalent bonds
• What is Graphene?

  A single layer of carbon atoms arranged in a hexagonal lattice, also known as one layer of graphite (same number of carbons bonded)
• Why can Diamond conduct heat?

  The carbon atoms are tightly packed together and rigid
• Is Diamonds melting point high or low and why?

  High because of strong covalent bonds between carbons
• What structure is Diamond and why?

  Tetrahedral because each carbon is bonded 4 times
• Give 3 examples of giant covalent structures

  Graphite, Graphene & Diamond
• Which other giant covalent molecule has the same structure as Diamond?

  Silicon
• Does Diamond conduct electricity and why?

  No because there are no delocalised electrons to carry a charge
• Is Diamond soluble and why?

  No because the covalent bonds are too strong to break
• What is one property of Diamond that makes it desirable for gemstones?

  It is hard
• Why can metals conduct electricity?

  Metal atoms donate their outer shell electrons forming metal ions and delocaised electrons which are free to move and carry a charge
• Do Giant Metallic Lattices have a high or low melting point and why?

  High due to the strong electrostatic attraction between the positive metal ions and negative delocalised electrons
• Are solid metals soluble and why?

  No because the electrostatic forces of attraction are too strong to break
• Why do some metals have higher melting points than others?

  The more electrons a metal atom can donate, the more delocalised electrons there are to carry a charge therefore the higher its melting point will be
• Why are metals good thermal conductors?

  The free delocalised electrons can transfer kinetic energy
• Using Period 3 as an example, what is general trend in melting point and why?

  General increase because the first 3 elements are metals which have increasing positive charges, increasing number of delocalised electrons and smaller ionic radius forming a stronger metallic bond
• Using Period 3 as an example, which element has the highest melting point and why?

  Silicon (Si) because its a giant covalent structure with strong covalent bonds
• Using Period 3 as an example, why does Phosphorus have a lower m.p than Silicon?

  It is a weaker simple molecular structure with weaker induced dipole-dipole forces
• Using Period 3 as an example, why does Sulphur have a higher melting point than Phosphorous?

  Sulphure (S8) is a larger simple molecular structure compared to P4 so has larger induced dipole-dipole forces
• Using Period 3 as an example, why does Chlorine have a lower m.p than Sulphur?

  Chlorine (Cl2) is a smaller simple molecular structure compared to S8 so has smaller incuded dipole-dipole forces