Group 7

• What are the elements in Group 7 called?

  Halogens
• What are some uses of halogens?

  • Water purification
  • Bleaching agents (chlorine)
  • Flame-retardants (bromine)
  • Antiseptic agents (iodine)
• How do the colors of Group 7 elements change?

  They get darker going down the group
• What does volatility refer to?

  How easily a substance can evaporate
• What happens to the melting and boiling points of Group 7 elements down the group?

  They increase going down the group
• What does the increase in boiling point indicate about volatility in Group 7 elements?

  Volatility decreases as boiling point increases
• Which halogen is the most volatile?

  Fluorine
• What type of molecules are halogens?

  Diatomic molecules
• How are covalent bonds formed in halogens?

  By overlapping their orbitals
• What happens to bond strength as you go down Group 7?

  Bond strength decreases going down the group
• What is bond enthalpy?

  Energy needed to break one mole of bonds
• What is the exception to the bond enthalpy trend in halogens?

  Fluorine has a smaller bond enthalpy
• Why does fluorine have a smaller bond enthalpy than chlorine and bromine?

  Lone pairs cause significant repulsion in fluorine
• What type of forces exist between halogen molecules?

  Weak van der Waals' forces
• How do van der Waals' forces change down the group?

  They increase due to more electrons
• What is the relationship between molecular size and volatility in halogens?

  Larger molecules have lower volatility
• What happens to the oxidising power of halogens down the group?

  It decreases going down the group
• How do halogens react with metals?

  By accepting an electron to become an ion
• What is the oxidation number of halogens when they gain an electron?

  It decreases
• What is the significance of electronegativity in halogens?

  It indicates how strongly they attract electrons
• How does atomic size affect the oxidising power of halogens?

  Larger size leads to decreased oxidising power
• What is a displacement reaction in halogens?

  A more reactive halogen displaces a less reactive one
• What is the ionic equation for chlorine displacing bromine?

  Cl (aq) + 2Br (aq) → 2Cl (aq) + Br (aq)
• How do halide ions act as reducing agents?

  By donating electrons to another atom
• What happens to the reducing power of halide ions down the group?

  It increases going down the group
• How does ionic radius affect the reducing power of halide ions?

  Larger ionic radius leads to increased reducing power
• What is the effect of shielding on the outermost electrons of halide ions?

  It makes them easier to lose electrons
• How can halide ions be identified in a solution?

  By adding silver nitrate solution
• Why is nitric acid added before silver nitrate in testing for halides?

  To prevent false positives from carbonate ions
• What is the ionic equation for the reaction of silver ions with halide ions?

  Ag (aq) + X (aq) → AgX (s)
• What color precipitate does silver chloride form?

  White precipitate
• What color precipitate does silver bromide form?

  Cream precipitate
• What color precipitate does silver iodide form?

  Yellow precipitate
• What are the characteristics of silver halide precipitates?

  • Dense
  • Characteristically coloured
• What is the significance of the term "halogen"?

  • Derived from Greek meaning "salt-maker"
  • Reflects their reaction with metals to form salts
• How can halide ions be identified in an unknown solution?

  By dissolving in nitric acid and adding silver nitrate
• Why is nitric acid used in the halide ion identification process?

  To prevent false positives from carbonate ions
• What is the ionic equation for the reaction of halide ions with silver nitrate?

  Ag (aq) + X (aq) → AgX (s)
• What happens if the unknown solution contains halide ions?

  A precipitate of silver halide will form
• What color is the precipitate formed by silver chloride?

  White