Open main menu


chemical element wi the atomic nummer o 19

Potassium is a chemical element wi seembol K (derived frae Neo-Latin, kalium) an atomic nummer 19. It wis first isolated frae potash, the ess o plants, frae which its name derives. In the periodic cairt, potassium is ane o the alkali metals. Aw o the alkali metals hae a single valence electron in the ooter electron shell, which is easily remuived tae creaut an ion wi a positive chairge – a cation, which combines wi anions tae form sauts. Potassium in naitur occurs anly in ionic sauts. Elemental potassium is a saft sillery-white alkali metal that oxidizes rapidly in air an reacts vigorously wi watter, generatin sufficient heat tae ignite hydrogen emittit in the reaction an burnin wi a lilac-colored flame. It is foond dissolved in sea watter (which is 0.04% potassium bi wecht[4][5]), an is pairt o mony meenerals.

Potassium,  19K
Potassium pearls (in paraffin ile, ~5 mm ilk)
General properties
Appearance sillery gray
Staundart atomic wecht (Ar, staundart) 39.0983(1)[1]
Potassium in the periodic cairt
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gowd Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium


Atomic nummer (Z) 19
Group group 1 (alkali metals)
Period period 4
Element category   alkali metal
Block s-block
Electron confeeguration [Ar] 4s1
Electrons per shell
2, 8, 8, 1
Pheesical properties
Phase (at STP) solit
Meltin pynt 336.7 K ​(63.5 °C, ​146.3 °F)
Bylin pynt 1032 K ​(759 °C, ​1398 °F)
Density (near r.t.) 0.862 g/cm3
when liquid (at m.p.) 0.828 g/cm3
Creetical pynt 2223 K, 16[2] MPa
Heat o fusion 2.33 kJ/mol
Heat o vapourisation 76.9 kJ/mol
Molar heat capacity 29.6 J/(mol·K)
Atomic properties
Oxidation states 1, −1 ​strangly basic oxide
Electronegativity Pauling scale: 0.82
Ionisation energies
Atomic radius empirical: 227 pm
Covalent radius 203±12 pm
Van der Waals radius 275 pm
Coloyr lines in a spectral range
Spectral lines o Potassium
Creestal structurbody-centred cubic (bcc)
Body-centered cubic creestal structur for potassium
Speed o soond thin rod 2000 m/s (at 20 °C)
Thermal expansion 83.3 µm/(m·K) (at 25 °C)
Thermal conductivity 102.5 W/(m·K)
Electrical resistivity 72 n Ω·m (at 20 °C)
Magnetic orderin paramagnetic[3]
Young's modulus 3.53 GPa
Shear modulus 1.3 GPa
Bouk modulus 3.1 GPa
Mohs haurdness 0.4
Brinell haurdness 0.363 MPa
CAS Nummer 7440-09-7
Diskivery Humphry Davy (1807)
First isolation Humphry Davy (1807)
Main isotopes o potassium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct
39K 93.26% stable 40K 0.012% 1.248(3)×109 y β 40Ca
ε 40Ar
β+ 40Ar
41K 6.73% stable
| references | in Wikidata

Naiturally occurrin potassium is componed o three isotopes, o which 40
is radioactive. Traces o 40
are foond in aw potassium, an it is the maist common radioisotope in the human bouk.

Potassium is chemically very seemilar tae sodium, the previous element in group 1 o the periodic table. Thay hae a seemilar first ionisation energy, which allows for each atom tae gie up its sole outer electron. That thay are different elements that combine wi the same anions tae mak seemilar salts wis suspected in 1702,[6] an wis proven in 1807 uisin electrolysis.

Maist industrial applications o potassium exploit the heich solubility in watter o potassium compoonds, sic as potassium saips. Hivy crop production rapidly depletes the sile o potassium, an this can be remedied wi agricultural fertilizers containin potassium, accoontin for 95% o global potassium chemical production.[7]

Potassium ions are necessar for the function o aw livin cells. The transfer o potassium ions throu nerve cell membranes is necessar for normal nerve transmission; potassium depletion can result in numerous abnormalities, includin an abnormal hert rhythm an various electrocardiographic (ECG) abnormalities. Fresh fruits an vegetables are guid dietar soorces o potassium. The body responds tae the influx o dietar potassium, which raises serum potassium levels, wi a shift o potassium frae ootside tae inside cells an an increase in potassium excretion bi the neers.


  1. Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305. 
  2. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nt ed.). CRC Press. p. 4.122. ISBN 1439855110. 
  3. Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. 
  4. Webb, D. A. (April 1939). "The Sodium and Potassium Content of Sea Water" (PDF). The Journal of Experimental Biology (2): 183. 
  5. Anthoni, J. (2006). "Detailed composition of seawater at 3.5% salinity". Retrieved 2011-09-23. 
  6. Marggraf, Andreas Siegmund (1761). Chymische Schriften. p. 167. 
  7. Greenwood, p. 73

Citit soorces

  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.