Difference between revisions of "Barium"
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==Properties== | ==Properties== | ||
===Chemical=== | ===Chemical=== | ||
| − | Barium slowly oxidizes in air to form a dark layer of [[barium oxide]] and barium nitride. Barium and its compounds burn with a green flame. | + | Barium slowly oxidizes in air to form a dark layer of [[barium oxide]] and barium nitride. Barium and its compounds burn with a green flame. This property allowed it to be used in green fireworks, though in recent years, boron compounds are beginning to replace barium, as they're less toxic. |
Barium is readily attacked by acids, though reaction with [[sulfuric acid]] forms a protective insoluble layer of [[barium sulfate]], which protects the metal from further corrosion. | Barium is readily attacked by acids, though reaction with [[sulfuric acid]] forms a protective insoluble layer of [[barium sulfate]], which protects the metal from further corrosion. | ||
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==Isolation== | ==Isolation== | ||
| − | Barium can be | + | Barium can be isolated through the aluminothermic reduction of [[barium oxide]]: |
| − | + | :4 BaO + 2 Al → 3 Ba↑ + BaAl<sub>2</sub>O<sub>4</sub> | |
| − | Due to the high temperatures released during this reaction, the resulting barium metal turns to vapors, which are condensed under [[argon]]. | + | Due to the high temperatures released during this reaction, the resulting barium metal turns to vapors, which are condensed under [[argon]]. This is not easy to do. |
[[Silicon]] can also be used as a reducing agent. | [[Silicon]] can also be used as a reducing agent. | ||
Latest revision as of 21:55, 14 May 2018
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Barium, Ba | ||||
| Appearance | Silvery-white metal | ||||
| Barium in the periodic table | |||||
| |||||
| Atomic number | 56 | ||||
| Standard atomic weight (Ar) | 137.327(7) | ||||
| Group, block | (alkaline earth metals); s-block | ||||
| Period | period 6 | ||||
| Electron configuration | [Xe] 6s2 | ||||
per shell | 2, 8, 18, 18, 8, 2 | ||||
| Physical properties | |||||
| Silvery-white | |||||
| Phase | Solid | ||||
| Melting point | 1000 K (727 °C, 1341 °F) | ||||
| Boiling point | 2118 K (1845 °C, 3353 °F) | ||||
| Density near r.t. | 3.51 g/cm3 | ||||
| when liquid, at | 3.338 g/cm3 | ||||
| Heat of fusion | 7.12 kJ/mol | ||||
| Heat of | 142 kJ/mol | ||||
| Molar heat capacity | 28.07 J/(mol·K) | ||||
| pressure | |||||
| Atomic properties | |||||
| Oxidation states | +2, +1 (a strongly basic oxide) | ||||
| Electronegativity | Pauling scale: 0.89 | ||||
| energies |
1st: 502.9 kJ/mol 2nd: 965.2 kJ/mol 3rd: 3600 kJ/mol | ||||
| Atomic radius | empirical: 222 pm | ||||
| Covalent radius | 215±11 pm | ||||
| Van der Waals radius | 268 pm | ||||
| Miscellanea | |||||
| Crystal structure | body-centered cubic | ||||
| Speed of sound thin rod | 1620 m/s (at 20 °C) | ||||
| Thermal expansion | 20.6 µm/(m·K) (at 25 °C) | ||||
| Thermal conductivity | 18.4 W/(m·K) | ||||
| Electrical resistivity | 332 Ω·m (at 20 °C) | ||||
| Magnetic ordering | Paramagnetic | ||||
| Young's modulus | 13 GPa | ||||
| Shear modulus | 4.9 GPa | ||||
| Bulk modulus | 9.6 GPa | ||||
| Mohs hardness | 1.25 | ||||
| CAS Registry Number | 7440-39-3 | ||||
| History | |||||
| Discovery | Carl Wilhelm Scheele (1772) | ||||
| First isolation | Humphry Davy (1808) | ||||
Barium is a chemical element with symbol Ba and atomic number 56. It is the heaviest non-radioactive s-block element.
Contents
Properties
Chemical
Barium slowly oxidizes in air to form a dark layer of barium oxide and barium nitride. Barium and its compounds burn with a green flame. This property allowed it to be used in green fireworks, though in recent years, boron compounds are beginning to replace barium, as they're less toxic.
Barium is readily attacked by acids, though reaction with sulfuric acid forms a protective insoluble layer of barium sulfate, which protects the metal from further corrosion.
Barium reacts with water to release hydrogen gas. Barium hydroxide precipitates:[1]
- Ba + 2 H2O → Ba(OH)2 + H2
The same reaction also happens with alcohols, giving barium alkoxide.
Barium reacts with ammonia to form complexes such as Ba(NH3)6.
Physical
Barium is a silvery white metal, that rapidly turns black on exposure with air. Barium melts at 730 °C, intermediate between those of the lighter strontium (780 °C) and heavier radium (700 °C). Its boiling point of 1,900 °C is higher than that of strontium (1,382 °C) and radium (~1737 °C). Barium has a density of 3.62 g/cm3
Availability
Barium metal is sold by various chemical suppliers, either under oil or ampouled. GalliumSource sells 50 g of barium at a price of $92.00.
Isolation
Barium can be isolated through the aluminothermic reduction of barium oxide:
- 4 BaO + 2 Al → 3 Ba↑ + BaAl2O4
Due to the high temperatures released during this reaction, the resulting barium metal turns to vapors, which are condensed under argon. This is not easy to do.
Silicon can also be used as a reducing agent.
Projects
- Make barium peroxide
- Make soluble barium salts
- Green flame
- Ellement collecting
Handling
Safety
Barium readily reacts with water releasing hydrogen gas, which is flammable and its build-up may cause explosions. However, unlike alkali metals, it can be safely handled with bare hand.
Soluble barium salts and other compounds are very toxic to organisms and should be handled with proper protection. Insoluble barium compounds however, are pretty much non-toxic .
Storage
Barium metal must be stored away from moisture, air and other corrosive vapors. It is best stored under mineral oil or ampouled, under argon.
Disposal
Barium metal is best converted to barium sulfate, which is non-toxic.
