Quick Facts
| Property | Value |
|---|---|
| Symbol | Ba |
| Atomic Number | 56 |
| Atomic Mass | 137.33 u |
| Category | Alkaline Earth Metal |
| Period | 6 |
| Group | 2 |
| Block | s |
| Electron Configuration | [Xe] 6s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 3.51 g/cm³ |
| Melting Point | 727°C (1000 K) |
| Boiling Point | 1845°C (2118 K) |
| Appearance | Silvery-gray metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Xe] 6s² |
| Electronegativity | 0.89 (Pauling scale) |
| First Ionization Energy | 502.9 kJ/mol |
| Atomic Radius | 222 pm |
| Covalent Radius | 215 pm |
| Van der Waals Radius | 268 pm |
History and Discovery
Discovered by: Carl Wilhelm Scheele (identified), Humphry Davy (isolated) Year of Discovery: 1774 (identified), 1808 (isolated) Location: Sweden and England
Etymology
Named from the Greek "barys" meaning "heavy," due to the high density of barium compounds like barite.
Discovery Story
Carl Wilhelm Scheele identified barium as a new element in 1774 by analyzing pyrolusite. Humphry Davy isolated barium metal in 1808 through electrolysis of molten barium hydroxide.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹³⁰Ba | 0.11% | Stable | - |
| ¹³²Ba | 0.10% | Stable | - |
| ¹³⁴Ba | 2.42% | Stable | - |
| ¹³⁵Ba | 6.59% | Stable | - |
| ¹³⁶Ba | 7.85% | Stable | - |
| ¹³⁷Ba | 11.23% | Stable | - |
| ¹³⁸Ba | 71.70% | Stable | - |
Occurrence
Natural Abundance
Barium comprises about 425 ppm of Earth's crust. Main ores are barite (BaSO₄) and witherite (BaCO₃). Major producers are China, India, and Morocco.
Extraction and Production
- Reduction: Of barium oxide with aluminum
- Electrolysis: Of molten barium chloride
- Sources: Barite mining
- Global barite production: about 8 million tons annually
Applications and Uses
Medical Applications
- Barium sulfate for X-ray contrast (barium meal/enema)
- Non-toxic when insoluble (sulfate form)
Industrial Applications
- Glass manufacturing (reduces glass shrinkage)
- Oil and gas drilling (barite as weighting agent)
- Rubber manufacturing
- Paint pigments (barium sulfate)
Chemical Applications
- Barium carbonate for ceramics
- Barium oxide in cathode ray tubes (historical)
- Vacuum tube getters
Other Uses
- Fireworks (green color)
- Rat poison (barium carbonate)
- Water softening
Biological Role
Barium has no biological role and is toxic to humans.
In the Human Body
Barium is not normally found in the body. Soluble barium compounds are toxic.
Toxicity
Soluble barium compounds are highly toxic, affecting the heart and muscles. Insoluble barium sulfate is safe for medical imaging.
Safety and Hazards
Toxicity
Soluble barium compounds are toxic. Barium sulfate is non-toxic. Barium chloride and carbonate are poisons.
Handling Precautions
- Metal reacts with air and water
- Store under oil or inert atmosphere
- Avoid ingestion of soluble barium compounds
- Use appropriate PPE
Environmental Impact
Barium compounds occur naturally in the environment. Industrial contamination can affect water supplies.
Interesting Facts
- Barium sulfate is so safe it's swallowed for X-ray imaging, despite barium being toxic
- Fireworks' green color often comes from barium compounds
- Barium was used in CRT televisions to remove residual gases
- Barite is used as a weighting agent in oil drilling mud
- The contrast between toxic barium chloride and safe barium sulfate illustrates the importance of solubility in toxicology