Name: potassium	Group number: 1
Symbol: K	Group name: Alkali metal
Atomic number: 19	Period number: 4
Atomic weight: 39.0983 (1)	Block: s-block
CAS Registry ID: 7440-09-7	Voice:
Standard state: solid at 298 K	Colour: silvery white
Classification: Metallic	Availability:

Isolation

Potassium would not normally be made in the laboratory as it is so readily available commercially. All syntheses require an electrolytic step as it is so difficult to add an electron to the poorly electronegative potassium ion K⁺.

Potassium is not made by the same method as sodium as might have been expected. This is because the potassium metal, once formed by electrolysis of liquid potassium chloride (KCl), is too soluble in the molten salt.

cathode: K⁺(l) + e^- K (l)

anode: Cl^-(l) ¹/₂Cl₂ (g) + e^-

Instead, it is made by the reaction of metallic sodium with molten potassium chloride at 850°C.

Na + KCl K + NaCl

This is an equilibrium reaction and under these conditions the potassium is highly volatile and removed from the system in a form relatively free from sodium impurities, allowing the reaction to proceed.