3.2.3 Group 7, the halogens

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  • Why is chlorine a better oxidising agent then iodine
    Chlorine has a smaller atomic radius, compared to Group 7 decreasing down, smaller shielding allows it to gain electrons, due to stronger attraction between valence electrons and the nucleus
  • What is a displacement reaction
    A more reactive metal will displace the less reactive metal from its salt
  • Why can't fluorine have a positive oxidation number
    Low atomic radius, high nuclear charge
  • Why is fluorine special in terms of electron affinity
    Low magnitude, electrons get too close, start repelling, less energy is released when electron is released when it eneters the outer shell.
  • Iodine
    Grey sold
  • Bromine
    Dark red/ brown, liquid
  • Chlorine at room temperature
    Green gas
  • Fluorineat room temperature
    Yellow gas
  • Why is ionic radius bigger
    Greater repulsion of electron within the radius u
  • Compare the atom and ionic size
    Ionic radius is larger than the size of the atom
  • Atomic radius trend
    It increases, more shells going down the group, more shielding, weaker attraction between the valence electron and the nucleus
  • Why is Fluorine weak
    The atoms are close to each other, repulsion between the non-bonding electrons causes it be weaker
  • Trend in the boiling point
    Increases down the group, more shells, more VDW, more energy to overcome the bonds, greater energy is needed, instantaneous dipole-dipole
  • Trend in electron affinity
    It decreases as it has a weaker attraction, bigger radius, and shielding, less exothermic
  • Trend in atomic radius
    It increases going down the group
  • Trend in electronegativity
    Increases up the group, and decreases down the group, atoms are bigger
  • Why can't halogens conduct electricity
    No free-charged particles that are free to move
  • Trend of reactivity down the group
    It decreases, becomes less reactive
  • What intermolecular forces occur between them
    Van de waals
  • Boiling point trend as it moves down the group
    It increases
  • Appearance of iodine solid
    Grey solid
  • What type of molecule are halogens
    Diatomic molecules
  • What block are they found in?
    Block P
  • Define disproportionation
    When a reaction has neither lost or gained electrons
  • Why are halogens oxidising agents?
    Removes electrons other elements, gains electrons, reduction
  • Why CI is a better oxidising agent than I
    Smaller atomic radius, smaller shielding, stronger attraction between valence electron and nucleus
  • Colour solution of CI and Br
    Yellow solution
  • Colour solution of CI and I
    Brown solution
  • Colour solution of Br and I
    Brown solution
  • How to test for iodine?
    Add starch, blue balck if present
  • Name the strongest oxidising agent
    Chlorine
  • Name the weakest oxidising agent
    Bromine
  • Colour of mixed solution CI2 and Br-
    Red, brown
  • Why can halides be called a reducing agent?
    They lose electrons via oxidiation
  • Why is Iodide a greater reducing agent than chlorine?
    More shielding, bigger ions, weaker nuclear attraction
  • How does Iodide look different to iodine at room temperature?
    White solid crystals
  • What is a precipitate reaction?
    2 solutions that react and form a salt
  • Halide ions react with silver nitrate to form?
    Silver halide precipitates
  • Method
    Add nitric acid to the solution being tested, add silver nitrate to the solution being tested, add ammonia to the precipitate
  • Why are we adding nitric acid
    Get rid of impurities of OH and CO3, would interfere with the test by creating preciptates