POTASSIUM

Discovery

Sir Humphry Davy discovered potassium in 1807 by the electrolysis of potassium hydroxide (potash). The metal collected at the cathode. This was the first metal isolated by electrolysis. The name potassium is from the English word 'potash', originally meaning an alkali extracted with water in a pot of ash of burnt wood or tree leaves.

Properties

Symbol: K Type:Alkali Metal Atomic weight:39.0983 Density @ 293 K:0.862 g/cm3

Atomic volume:45.46 cm3/mol

States and Appearance

State (s, l, g):solid Melting point:336.5 K (63.4 °C)/Boiling

point:1038.7 K (765.6 °C) Structure:bcc: body-centered cubic Color:silvery-white Hardness:0.4 mohs

Energies

Specific heat capacity:0.75 J g-1 K-1

Heat of atomization:89 kJ mol-1 Heat of fusion:2.334 kJ mol-1 Heat of vaporization :79.870 kJ mol-1 1st ionization energy:418.8 kJ mol-1 2nd ionization energy:3051.3 kJ mol-1 3rd ionization energy:4411.3 kJ mol-1 Electron affinity:48.385 kJ mol-1

Oxidation and electrons

Shells:2,8,8,1 Electron configuration: [Ar] 4s1

Minimum oxidation number: 0 Maximum oxidation number:1 Min. common oxidation no.: 0 Max. common oxidation no.:1 Electronegativity (Pauling

Scale):0.82 Polarizability volume:43.4 Å3

Characteristics

Harmful effects:Potassium is considered to be non-toxic. Due to its highly reactive nature, elemental potassium must be handled with extreme care.

Characteristics: Potassium is silvery-white, low melting, metal soft enough to be easily cut with a knife. It tarnishes rapidly in air, forming a dull oxide coating. 

Potassium burns with a lilac colored flame. It is extremely reactive, reacting violently with water, for example, to produce hydrogen gas and potassium hydroxide.

Uses

Potassium is essential for plant growth. Plants use it, for example, to make proteins, hence the greatest demand for potassium compounds is in fertilizers. 

Potassium hydroxide is a strong alkali and an important industrial chemical. It is used in the manufacture of soft soaps and as an electrolyte in alkaline batteries.

Potassium chloride is used as a healthier alternative to table salt.

Toughened glass can be made by immersing glass in molten potassium nitrate.

Potassium nitrate is the main explosive ingredient in gunpowder.

Reactions

Reaction with air:vigorous, ⇒ KO2

Reaction with 6 M HCl:vigorous, ⇒ H2, KCl

Reaction with 15 M HNO3:vigorous, ⇒ H2, NOx, KNO3

Reaction with 6 M NaOH:vigorous, ⇒ H2, KOH

Compounds

Oxide(s): K2O Chloride(s):KCl Hydride(s): KH

Radius

Atomic radius:220 pm Ionic radius (1+ ion):152 pm Ionic radius (2+ ion):pm Ionic radius (3+ ion):pm Ionic radius (2- ion):pm Ionic radius (1- ion):pm

Conductivity

Thermal conductivity:102.5 W m-1 K-1

Electrical conductivity:0.164 x 106 S cm-1

Abundance and isotopes

Abundance earth's crust:2.1 % by weight, 1.6 % by moles

Abundance solar system:4 parts per million by weight, 100 parts per billion by moles

Cost, pure:$100 per 100g Cost, bulk:$65 per 100g Source:Potassium does not occur as a free element in

nature; it is too reactive, forming compounds from which it is difficult to separate. Potassium is obtained commercially by electrolysis of potassium hydroxide or potassium chloride

Isotopes:Potassium has 20 isotopes whose half-lives are known, with mass numbers 35 to 54. Of these, two are stable, 39K, and 41K. Over 93.2% of naturally occurring potassium is in the form of 39K.

Lab and other uses

It makes good explosions and is oftenly used to react with water in lab experiments though if it gets into the sink it means a hole drilled all the way through the water pipe.

Its not strong enough to be made into a bomb, unless its for a less impactful bomb.(Francium is more commonly used for a bomb but in extremely small quantities)