Potassium compounds: potassium iodide

potassium symbol icon

The potassium in potassium iodide formally is in the oxidation state 1.

Crystal structure of potassium iodide

Potassium iodide

  • Formula as often written: KI
  • Hill system formula: I1K1
  • CAS registry number: [7681-11-0]
  • Formula weight: 166.003
  • Class: iodide


  • potassium iodide
  • potassium(I) iodide

Physical properties

  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 681°C
  • Boiling point: 1323°C
  • Density: 3120 kg m-3


Coming soon...

Element analysis

Element percentages for the elements in potassium iodide
Element %
I 76.45
K 23.55


One way to make potassium iodide is to react the hydroxide with hydroiodic acid. The resulting salt can then be purified by recrystallization.

KOH(aq) + HI(aq) → KI(aq) + H2O(l)

While not a normal route of preparation because of the expense, potassium metal reacts vigorously with all the halogens to form potassium halides. So, it burns with iodine, I2, to form potassium(I) iodide, KI.

2K(s) + I2(s) → 2KI(s)

Solid state structure

  • Geometry of potassium: 6 coordinate: octahedral
  • Prototypical structure: NaCl (rock salt)

Crystal structure of potassium iodide

Isotope pattern

What follows is the calculated isotope pattern for the KI unit with the most intense ion set to 100%.

Formula: K1I1

mass  %
166 100.0 __________________________________________________
167 0.0
168 7.2 ____


The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

WebElements Shop

WebElements now has a WebElements shop at which you can buy periodic table posters, mugs, T-shirts, games, fridge magnets, molecular models, and more.

Periodic Table fridge magnets Periodic Table fridge magnets
Buy our periodic table fridge magnets here

WebElements poster Periodic table t-shirts Periodic table mouse mats Molymod molecular model kits Chemistry educational resources

potassium atomic number