Barium Element Properties
Complete reference for Barium (Ba, element 56): atomic data, electron configuration, isotopes, physical constants, oxidation states, and chemical behavior.
Barium
Alkaline Earth Metal — Period 6, Group 2
Atomic Identity
Electron Configuration
No unpaired electrons — readily loses 2e⁻ to form Ba²⁺
Oxidation States
| Oxidation State | Occurrence | Example Compounds | Notes |
|---|---|---|---|
| 0 | Elemental | Ba metal | Ground state — reactive metal stored under mineral oil |
| +2 | Most Common | BaCl₂, BaSO₄, BaO, Ba(OH)₂, BaCO₃ | Only common ionic state; forms Ba²⁺ by losing both 6s electrons |
Unlike transition metals, barium exhibits only two oxidation states. The +2 state is overwhelmingly dominant in all naturally occurring and industrially synthesized barium compounds.
Isotopes of Barium
| Isotope | Symbol | Protons | Neutrons | Mass (u) | Abundance | Stability |
|---|---|---|---|---|---|---|
| Barium-130 | ¹³⁰Ba | 56 | 74 | 129.9063208 | 0.106% | Stable |
| Barium-132 | ¹³²Ba | 56 | 76 | 131.9050611 | 0.101% | Stable |
| Barium-134 | ¹³⁴Ba | 56 | 78 | 133.9045084 | 2.417% | Stable |
| Barium-135 | ¹³⁵Ba | 56 | 79 | 134.9056886 | 6.592% | Stable |
| Barium-136 | ¹³⁶Ba | 56 | 80 | 135.9045759 | 7.854% | Stable |
| Barium-137 | ¹³⁷Ba | 56 | 81 | 136.9058274 | 11.232% | Stable |
| Barium-138 | ¹³⁸Ba | 56 | 82 | 137.9052472 | 71.698% | Stable |
| Barium-133 | ¹³³Ba | 56 | 77 | 132.9060075 | Radioactive |
Unstable
EC decay, t½ = 10.51 y |
| Barium-140 | ¹⁴⁰Ba | 56 | 84 | 139.9106065 | Radioactive |
Unstable
β⁻ decay, t½ = 12.75 d |
Barium has 7 stable isotopes — one of the largest counts of any element — due to the magic neutron number 82 providing exceptional nuclear stability in this region of the periodic table.
Physical Properties
Chemical Properties
Ground State Quantum Numbers
Notable Emission Lines
Barium produces an apple-green to yellow-green flame in a flame test — one of the most recognizable flame colors in qualitative analysis — due to Ba⁺ emission lines around 514–524 nm.
Key Facts About Barium
Medical Contrast Agent
Barium sulfate (BaSO₄) is the standard oral and rectal contrast agent for X-ray and fluoroscopic imaging of the gastrointestinal tract. It is insoluble in water and the body, making it safe to ingest despite the toxicity of soluble barium salts.
Green Fireworks
Barium chlorate (Ba(ClO₃)₂) and barium nitrate (Ba(NO₃)₂) are pyrotechnic oxidizers that produce a vivid green color in fireworks, flares, and tracers. The green flame arises from excited Ba⁺ ions emitting near 514–524 nm.
Piezoelectric Ceramic
Barium titanate (BaTiO₃) was the first ceramic found to exhibit ferroelectricity and piezoelectricity after WWII. It remains a key material in capacitors, sensors, actuators, and ultrasonic transducers, underpinning modern electronics.
Highly Reactive Metal
Barium reacts vigorously with water, oxygen, and halogens. Freshly cut barium metal oxidizes rapidly in air, forming a yellow-white surface layer of barium oxide and barium peroxide (BaO₂). It must be stored under mineral oil or inert gas to prevent ignition.
Geochemical Tracer
Barium isotope ratios (especially ¹³⁸Ba/¹³⁴Ba) are used as geochemical tracers to study ocean circulation, marine barite (BaSO₄) precipitation, and carbonate system dynamics. Ba/Ca ratios in coral skeletons record past riverine input and upwelling history.
Soluble Salt Toxicity
Soluble barium salts are toxic by competitive inhibition of potassium channels, causing severe hypokalemia, muscle weakness, and potentially fatal cardiac arrhythmia. The antidote is intravenous potassium chloride. Occupational exposure is regulated by OSHA at 0.5 mg/m³ (TWA).
Summary
Complete reference for Barium (Ba, element 56): atomic data, electron configuration, isotopes, physical constants, oxidation states, and chemical behavior.
How it works
- Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
- Check the electron configuration panel for orbital notation and quantum numbers.
- Review the isotopes table for stable barium isotopes with natural abundance data.
- Consult the physical properties panel for melting point, density, and state at STP.
- Use the chemical properties section to understand alkaline earth metal behavior and ionization energies.
- Copy any value with one click for use in reports or calculations.
Use cases
- Look up barium constants for chemistry homework or exams.
- Verify atomic data when writing lab reports.
- Reference isotope masses for nuclear chemistry or geochemistry research.
- Check thermodynamic constants for materials science or engineering.
- Teach or learn alkaline earth metal properties using barium as an example.
- Confirm electron configuration before writing molecular orbital diagrams.
- Compare barium isotopes for radiological dating or environmental analysis.
- Quick-reference ionization energy for electrochemistry or spectroscopy work.