Group 7

• What is the electron configuration of Cl?

  $1s^22s^22p^63s^23p^5$
• What is the electron configuration of Cl-?

  $1s^22s^22p^63s^23p^6$
• What does electronegativity mean?

  The ability of an atom to attract the shared pair of electrons from a covalent bond
• Does electronegativity increase or decrease up the group?

  Increases up the group
• What is the most electronegative element?

  Fluorine
• Why is fluorine the most electronegative?

  More protons so more attraction for shared pair of electrons

  Shared pair of electrons closer to the nucleus (less shielded)
• Does the size of the atoms increase or decrease down the group?

  Increase, more electron energy levels
• What is the trend in melting points/boiling points?

  Increases down the group
• Why does mpt/bpt increase?

  VDW forces gets stringer down the group because molecules are larger and have more electrons so stronger VDW forces between molecules.
• What is the trend in colour down the group?

  Darker down the group
• What colour is F2 (g)?

  pale yellow
• What colour is Cl2 (g)?

  yellow/green
• What colour is Br2 (l)?

  brown/orange
• What colour is I2 (s)?

  black
• What colour is At2 (s)?

  black
• What is the colour of I2 (aq)?

  brown
• What is the colour of I2 (g)?

  purple
• Halogens are oxidising agents, what does this mean?

  They are electron acceptors/ gain electrons
• What is the best at gaining electrons?

  Fluorine
• Why is Fluorine the best at gaining electrons?

  small/less shielding/ outer shell closer to the nucleus
• How can you show the relative oxidising ability?

  Doing halogen displacement reactions
• What are the oxidising and reducing agents in this reaction: $F2\ \left(aq\right)+$$2KCl\ \left(aq\right)\ \rightarrow\ 2KF\ \left(aq\right)+$$Cl2\ \left(aq\right)$


  $2e^-+$$F2\ \rightarrow\ 2F^-$ -> F2 is the oxidising agent (reduced is gaining electrons)

  $2Cl^-\ \rightarrow\ Cl2\ +$$2e^-$ -> KCl is the reducing agent (oxidation is loss of electrons)
• What is the colour change of this reaction: $Cl2\ +$$\ 2KBr\ \rightarrow2KCl\ +$$Br2$


  yellow/green solution -> orange solution
• What is the test for aqueous halide ions?

  • Add some dilte nitric acid, to remove carbonate pr hydroxide impurities otherwise Ag2CO3 or AgOH precipitates are made
  • Add a few drops of AgNO3 (aq)
  • Add dilute ammonia solution and the AgCl precipitate dissolves to make a colourless solution
  • To remaining precipitates add concerntrated ammonia. The AgBr precipitate dissolves to make a colourless solution
  • AgI precipitate does not dissolve in either
• What is the ionic equation for AgNO3 and F? What is the colout of the solution?

  $F^-+$$Ag^+$$\rightarrow AgF\ \left(aq\right)$

  colourless solution
• What is the ionic equation for AgNO3 and Cl? What is the colour of the precipitate?

  $Cl^-+$$Ag^+$$\rightarrow AgCl\ \left(s\right)$

  white precipitate
• What is the ionic equation for AgNO3 and Br? What is the colour of the precipitate?

  $Br^-+$$Ag^+$$\rightarrow AgBr\ \left(s\right)$

  cream precipitate
• What is the ionic equation for AgNO3 and I? What is the colour of the precipitate?

  $I^-+$$Ag^+$$\rightarrow AgI\ \left(s\right)$

  yellow precipitate
• What does using halide ions as reducing agents mean?

  electron donors/losing electrons
• What is the order of the best reducing agents?

  best $I^->Br^->Cl^->F^-$ worst
• Why is this the order of redusing agents?

  Bigger molecules, electrons further from the nucleus so more shielded and therefore easier to lose
• How do you show the ability of reducing agents?

  Add solid sodium halides to concentrated H2SO4 (use a fume cupboard)
• What is the equation for NaF with H2SO4?

  $NaF\ \left(s\right)\ +$$H2SO4\ \left(l\right)\rightarrow NaHSO4\ \left(s\right)\ +$$HF\ \left(g\right)$
• What are the observations with NaF?

  steamy fumes of HF gas (an acidic gas)
• Is NaF with H2SO4 a redox reaction?

  No. Nothing changes oxidation state F- are not good enough reducing agent to reduce S
• What is the equation for NaCl with H2SO4?

  $NaCL\ \left(s\right)+$$H2SO4\ \left(l\right)\rightarrow NaHSO4\ \left(s\right)+$$HCl\ \left(g\right)$
• What are the observations with NaCl?

  steamy fumes of HCl gas (an acidic gas)
• Is NaCl with H2SO4 a redox reaction?

  No. Nothing changes oxidation state Cl- are not good enough reducing agents to reduce S
• What is the equation for NaBr with H2SO4?

  $NaBr\ \left(s\right)+$$H2SO4\ \left(l\right)\rightarrow NaHSO4\ \left(s\right)\ +$$HBr\ \left(g\right)$
• What are the observations with NaBr?

  see steamy fumes of HBr gas (an acidic gas)