- Materials
- Forms
- Reference Materials
-
Services
-
Services
-
-
Sectors
-
Supporting cutting edge research and development with advanced materials to your needs.
High performance materials for extreme conditions.
Innovative and lightweight materials with high mechanical properties and durability.
Materials used in chemical engineering from consumables to innovative solutions.
Advanced materials characterized by high electrical or insulation performance.
High quality materials for renewable energy.
Biocompatible and biodegradable materials to the highest standards.
High purity, biocompatible materials for high performance devices and applications.
High purity metals and alloys in various forms and crucibles suitable to your needs.
State of the art materials for the next generation of technologies.
High performance materials for extreme conditions.
Durable materials for corrosive environments.
Foils, disks or windows across a range of materials to facilitate your innovation.
Polymers, metal foils, and sustainable materials for your packaging needs.
Your requirements for unique products and attributes will be met across our 170,000+ product range and customization capabilities.
High-quality materials across branded products in various forms including rods, wires, and foils support space technology needs.
Highest quality materials to support your need for small-quantity specialist materials such as graphite and lithium compounds.
High purity materials to improve the reproducibility and reliability of your evaporation processes.
Academia Aerospace & Aeronautical Automotive Chemical Manufacturing Electronics and Bioelectronics Fuel Cells & Hydrogen Life Science and Biomaterials Storage & Batteries Vacuum Technology Mining and Metals Nanomaterials Nuclear Oil & Gas Optics Packaging Research & Labs Space Technology Medical Devices
-
- Brands
-
Resources
-
Find out our latest news.
Read our latest insights, and opinions.
Discover our Innovation Discovered podcasts on innovation, products, interesting topics, and more.
Find out how we've worked with our partners
Our latest updates on what we are doing, find out more.
Find out more about us and the great roles we have available for talented individuals. Find out more.
Take a look at our global distributors.
Explore our FAQ resource to help answer your key questions.
Gain a clearer picture of the language used in scientific study
-
- About Us
Caesium
Caesium (Cs, also known as cesium) is a soft, silvery-golden alkali metal with one of the lowest melting points among metallic elements, transitioning to liquid just above room temperature. Highly reactive—especially with air and water—it’s best stored under inert gas or oil. Caesium is prized in precision technology, vacuum electronics, and specialized industrial and nuclear applications.
Goodfellow’s caesium product range, which includes high-purity Caesium Pellets, is used widely for advanced laboratory research and industrial applications. Known for its photoelectric properties and low ionization energy, caesium is widely used in photoelectron spectroscopy, atomic clocks, and ion propulsion systems. It plays a key role in catalysis and optoelectronics, contributing to advancements in energy storage and precision measurement technologies. Well-suited for studies in quantum mechanics and advanced optics, caesium supports significant progress in material science and space exploration.
Properties
Identifiers
Isotopes
Applications
Grades
Synonyms
General Properties
| Property | Value |
|---|---|
| Atomic Number | 55 |
| Density | 1.88 g/cm³ |
| Melting Point | 28.44 °C |
| Boiling Point | 671 °C |
| Thermal Conductivity | 36 W/m·K |
| Electrical Resistivity | 2×10⁻⁷ Ω·m |
| Crystal Structure | Body-Centered Cubic (BCC) |
Chemical Properties
| Property | Value |
|---|---|
| Ionization Energy | 3.894 eV |
| Electronegativity (Pauling) | 0.79 |
| Oxidation State | +1 |
| Electrode Potential | –3.03 V |
| Reactivity | Pyrophoric in air; reacts explosively with water |
| Identifier | Value |
|---|---|
| Symbol | Cs |
| Atomic Number | 55 |
| CAS Number | 7440-46-2 |
| EC Number | 231-155-4 |
| UN Number | UN1407 (solid) |
| Isotope | Type | Notes |
|---|---|---|
| Cs‑133 | Stable | 100% natural—used in atomic clocks and NMR |
| Cs‑137 | Radioactive | Half‑life ~30.17 years; used in medical, industrial, hydrology |
Scientific Applications
| Use Case | Description |
|---|---|
| Atomic Clocks | Defines the SI second via Cs‑133 hyperfine transition |
| Vacuum Electronics | Used as a getter and coating in vacuum tubes |
| Mass Spectrometry | Ion source standard and calibration |
| Environmental Tracing | Radioactive isotopes track hydrological and fallout processes |
Industrial Applications
| Use Case | Description |
|---|---|
| Drilling Fluids | Caesium formate brines used in oil/gas well operations |
| Optical Glass | Infrared-grade glass, sensors, detectors |
| Ion Propulsion | Propellant in satellite ion thrusters |
| Catalysis | Used in chemical synthesis (e.g., sulfuric acid production) |
| Radiography & Therapy | Cs‑137 sources for radiotherapy and industrial gauges |
| Grade | Purity | Main Use |
|---|---|---|
| High Purity Caesium | 99.9% | Ideal for atomic clocks, vacuum electronics, precision instrumentation |
| Synonym |
|---|
| Cs |
| Cesium |
| Caesium Metal |
| Cesium Metal |