Potassium • Alkali Metal

Primary XPS region: K2p
Overlapping regions: C1s
Binding energies of common chemical states:

Chemical state	Binding energy K2p_3/2 / eV
KCl	292.9
KBr	293.2

Charge referenced to adventitious C1s peak at 284.8eV

Experimental Information

Often quicker to acquire C1s region and extend range to 305eV to capture K2p region.

Interpretation of XPS spectra

K2p peak has clearly spaced spin-orbit components (Δ_chloride=2.8eV).

Weaker K2p peaks can be easily confused with either C1s (CF₂) peaks or C1s satellite structure in aromatic compounds.
- Assignment of K2p versus C1s feature is possible by identifying spin-orbit components expected for K2p. Also check for K2s peak, binding energy ~378eV.

General comments

Since potassium is a highly reactive metal, it is always present as a compound, e.g., oxide.

About This Element

Symbol: K
Date of Discovery: 1807
Name Origin: English potash
Appearance: silvery
Discoverer: Sir Humphry Davy
Obtained From: carnallite

Melting Point: 336.53 K
Boiling Point: 1032 K
Density[kg/m3]: 856
Molar Volume: 45.94 × 10-6 m3/mol
Protons/Electrons: 19
Neutrons: 20
Shell Structure: 2,8,8,1
Electron Configuration: [Ar]4s1
Oxidation State: 1
Crystal Structure: Cubic Body Centered

Potassium, the second lightest metal, was discovered by Sir Humphry Davy in 1807. It reacts violently with water and can even catch fire spontaneously in water. It can be found bound to other elements in seawater and minerals and is needed for plant growth. Potassium is commonly used in fertilizer. It is also used in gunpowder and glass and plays a vital role in animal cells as one of the partners in the Na-K pump. K-40 decays into Ar-40 and this process is used in the dating of rocks.