The reactivity series

Rusting of Iron Nails

Despite the confusion in some revision books, the electrochemical and reactivity series is not the same.
The reactivity series is about:

• List of metals (sometimes with hydrogen and carbon added as baseline) arranged by the ability to reduce other chemicals in non-specific way.
• The reactivity is dependent on the conditions of the reactions and all are relative.
• So the order will be slightly different between various books and research. (However, generally it should be the same)
• Reactivity series
  K, *Na, *Ca,  Mg, Al, Zn, Fe, Sn, Pb, Cu, Hg, Ag, Au
  <—- increase in reactivity of metals.
  Do take notes with the *, the position of the calcium and sodium are different. In electrochemical series, calcium is more electropositive than sodium but not for the reactivity series.

This is in contract with the electrochemical series :

• List of reducing agents arranged by the way of negative potential in an electrochemical cell
• The conditions are pressure of 1 atm, temperature of 298 K and molar concentration of 1.o M
• The electrochemical series / electropositivity of metal
  

  Equilibrium	Eɵ (volts)
  Li+ (aq) + e <—> Li (s)	- 3.03
  K+ (aq) + e <—> K (s)	- 2.92
  *Ca2+ (aq) + 2e <—> Ca (s)	- 2.87
  *Na+ (aq) + e <—> Na (s)	- 2.71
  Mg2+ (aq) + 2e <—> Mg (s)	- 2.37
  Al3+ (aq) + 3e <—> Al (s)	- 1.66
  Zn2+ (aq) + 2e <—> Zn (s)	- 0.76
  Fe2+ (aq) + 2e <—> Fe (s)	- 0.44
  Pb2+ (aq) + 2e <—> Pb (s)	- 0.13
  2H+ (aq) + 2e <—> H2 (g)	0
  Cu2+ (aq) + 2e <—> Cu (s)	+ 0.34
  Ag+ (aq) + e <—> Ag (s)	+ 0.80
  Au3+ (aq) + 3e <—> Au (s)	+ 1.50

So, more IMPORTANTLY, the SPM syllabus focuses on the reactivity instead of electrochemical potentials, so do use the reactivity series instead of the electrochemical series.
Displacement of Halogen (Group 17) from Its Halide Solution
Halogen – elements in Group 17 of the Periodic Table
Example: chlorine, bromine and iodine.
Halogen Identification

Halogen	Colour in (conc.) aq. solution	Colour in (dilute) aq. solution	Colour in 1,1,1-trichloroethane
Iodine	Reddish-brown	Yellow	Purple
Bromine	Brown	Yellow	Brown
Chlorine	Pale yellow	Colourless	Colourless

Strength of oxidising agent in halogen
Cl₂, Br₂. I₂
<——— Oxidising power increases

Halide / Halogen	Chlorine	Bromine	Iodine
Potassium chloride	-	No changes	No changes
Potassium bromide	Chlorine displace bromine from KBr solution	-	No changes
Potassium iodide	Chlorine displace iodine from KI solution	Bromine displace iodine from KI solution	-