| Formula / Notation | Cs |
|---|---|
| CAS Number | 7440-46-2 |
| Molecular Weight | 132.91 |
| Melting Point | 28.5 |
| Boiling Point | 671.0 |
| Density | 1.93 |
| Solubility | Reacts explosively with water |
| Appearance | Soft, gold-coloured, liquid just above room temperature |
| Also Known As | Cs, cesium, caesium metal |
| Category | Elements |
What is Caesium?
Caesium is a soft, gold-coloured alkali metal, atomic number 55. Has the lowest ionisation energy and electronegativity of any stable element. The caesium atomic clock defines the second (SI). Caesium-133 hyperfine transition = 9,192,631,770 Hz.
Formula & Notation
IUPAC Name: Caesium
Other Names / Synonyms: Cs, cesium, caesium metal
Properties & Characteristics
Physical Data
| Property | Value |
|---|---|
| Melting Point | 28.5 |
| Boiling Point | 671.0 |
| Density | 1.93 |
| Molecular Weight | 132.91 |
| Solubility | Reacts explosively with water |
| Appearance | Soft, gold-coloured, liquid just above room temperature |
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
Caesium is a soft, gold-coloured alkali metal, atomic number 55. Has the lowest ionisation energy and electronegativity of any stable element. The caesium atomic clock defines the second (SI). Caesium-133 hyperfine transition = 9,192,631,770 Hz.
Atomic clocks (primary frequency standard - defines the SI second). Photoelectric cells (low work function). Ion propulsion engines (spacecraft). Drilling fluid additive (CsOH). Cs-137: radiation therapy and industrial gauges.
Reacts explosively with water. Ignites spontaneously in air. Causes severe chemical burns. More reactive than rubidium and potassium. Cs-137 (radioactive): major gamma emitter, significant accident hazard (Goiania 1987 incident). Store under inert gas.
The formula or notation for Caesium is: Cs