potassium

Name potassium
Symbol K
Atomic Weight 39.0983
Atomic Number 19
CAS ID 7440-09-7
Group Number 1
Group Name Alkali Metal
Period Number 4
Origin of Name English, potash; Latin kalium.
Year Discovered 1807
Discovery Credits Sir Humphry Davy at London, UK.
Class Metallic
Color Silvery White
Standard State Solid at 77 F & 298 K
Description Soft white metal, silvery when cut but reacts rapidly with oxygen and vigorously with water. Metal obtained from NaCl + KCl at 1100 K. Used in fertilizers, chemicals, and glass.

Diagnostic tests: 
In solution, a potassium will give a violet flame test color. This flame test will be contaminated with the colors of the other alkaline elements which are present in the sample. The test is best observed through a blue filter to suppress the yellow sodium flame.

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