Group 7 elements:  Redox reactions:

Physical properties:

 

Periodic Table

Electronic configuration:

  • Each Group 7 element has 7 electrons in the outer shell.
  • Each have s2 p5 configuration, and known are p block elements.
  • The require 1 electron to complete their outer shell

 

 

Halogens as oxidising agents:

 

1/2Cl2(g) + e- Cl-(g)

 

Oxidation

            Is

            Loss of electrons

 

            Reduction

            Is

            Gain of electrons

Explanation:

Animation

Redox reactions of the halogens:

Halogen In water In cyclohexane
Cl2 Pale green Pale Green
Br2 Orange Orange
I2 Brown Violet

Practical

Interpretation:

Animation

 

1                       Cl2(aq)         +          2Br-(aq)                 2Cl-(aq)            +             Br2(aq)

                       Pale green                                                                                            Orange

                                                                                                                                       Orange (CH)

 

2                       Cl2(aq)         +          2I-(aq)                    2Cl-(aq)            +             I2(aq)

                      Pale green                                                                                             Brown

                                                                                                                                       Purple (CH)

 

3                       Br2(aq)         +          2I-(aq)                     2Br-(aq)            +             I2(aq)

                         Orange                                                                                                 Brown

                                                                                                                                        Violet (CH)

                       Cl2(aq)         +          2Br-(aq)                 2Cl-(aq)            +             Br2(aq)

 

Element Cl2(aq) +  2Br-(aq) 2Cl-(aq) + Br2(aq) Change in Ox No Redox
Up Down
Cl 0       -1       1 Red
Br     -1       0 1   Ox

Disproportionation

 

            This is a reaction when the same element has been both oxidised and reduced

 

Disproportionation of chlorine in water (Bleach):

 

       Cl2(aq)      +       2H2O(l)              HCl(aq)           +       HClO(aq)

 

Element Cl2(aq) +  2H2O(l) HCl(aq) +

HClO(aq)

Change in Ox No Redox
Up Down
Cl 0       -1       1 Red
Cl 0           +1 1   Ox

Disproportionation of chlorine in aq sodium hydroxide:

 

Cl2(aq)      +       2NaOH(aq)              NaCl(aq)           +       NaClO(aq)         +          H2O(l)

          0                                                            -1                            +1

 

Element Cl2(aq) +  2NaOH(aq) NaCl(aq)  +

NaClO(aq)

+ H2O(l) Change in Ox No Redox
Up Down
Cl 0       -1           1 Red
Cl 0           +1     1   Ox

Disp Rxns

Questions 1 - 2  P 93

Group 7 elements:  Uses and halide tests

Properties of Group 7 elements and compounds:

Fluorine:

Halides:

Halide compound(s) Use
NaCl Table salt
NaF / SnF2 Toothpaste
CaF2 (Fluorite / fluorspar) Used to make lenses to focus IR light

Testing for Halide ions:

Practical

 

Interpretation:

 

Chloride: Ag+(aq) + Cl-(aq) AgCl(s) White precipitate Soluble in dilute NH3
Bromide: Ag+(aq) + Br-(aq) AgBr(s) Cream precipitate Soluble in conc NH3
Iodide: Ag+(aq) + I-(aq) AgI(s) Yellow precipitate Insoluble in conc NH3

Halide tests

 

Question 1 - 3  P95  /  5,6,7,8,10 and 14  P97  /  5,6 and 7  P99