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Oxidation & Electrons | Appearance & Characteristics Reactions | Compounds | Radius | Conductivity Abundance & Isotopes 
Rubidium in a glass tube (Photo: Dennis S.K, GNU Free Documentation License). |
General:
| Name: Rubidium | Symbol: Rb |
| Type: Alkali Metal | Atomic weight: 85.467 |
| Density @ 293 K: 1.53 g/cm3 | Atomic volume: 55.9 cm3/mol |
| Discovered: Rubidium was discovered in 1861 in the mineral lepidolite by Robert Bunsen and Gustav Kirchhoff using spectroscopic analysis. The element name comes from the Latin word 'rubidius', meaning deepest red. | |
States
| State (s, l, g): solid | |
| Melting point: 312.45 K (39.3 oC) | Boiling point: 963 K (690 oC) |
Energies
| Specific heat capacity: 0.363 J g-1 K-1 | Heat of atomization: 81 kJ mol-1 |
| Heat of fusion: 2.192 kJ mol-1 | Heat of vaporization : 72.216 kJ mol-1 |
| 1st ionization energy: 403 kJ mol-1 | 2nd ionization energy: 2632.1 kJ mol-1 |
| 3rd ionization energy: 3859.4 kJ mol-1 | Electron affinity: 46.885 kJ mol-1 |
Oxidation & Electrons
| Shells: 2,8,18,8,1 | Electron configuration: [Kr]5s1 |
| Minimum oxidation number: 0 | Maximum oxidation number: 1 |
| Min. common oxidation no.: 0 | Max. common oxidation no.: 1 |
| Electronegativity (Pauling Scale): 0.82 | Polarizability volume: 47.3 Å3 |
Appearance & Characteristics
| Structure: bcc: body-centered cubic | Color: silvery-white |
| Harmful effects: Rubidium is not known to be toxic. | Hardness: 0.3 mohs |
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Characteristics: Rubidium is a soft, silvery-white metallic element. It is solid at room temperature but melts easily, at 39.3 oC. Like the other group 1 metals, rubidium reacts violently in water, forming corrosive rubidium hydroxide (RbOH) and hydrogen gas, which is ignited by the heat of the reaction. Rubidium can also ignite spontaneously in air. It forms alloys with cesium, gold, sodium, and potassium and it forms amalgams with mercury. Rubidium burns with a reddish-violet flame color. Uses: Rubidium is used in photocells, as a getter (remover of trace gases) in vacuum tubes and as working fluid in vapor turbines. 87Rb has been used extensively in dating rocks. Rubidium compounds give a purple color in fireworks. Rubidium salts are used in glasses and ceramics. |
Reactions
| Reaction with air: vigorous, ⇒ RbO2 | Reaction with 6 M HCl: vigorous, ⇒ H2, RbCl |
| Reaction with 15 M HNO3: vigorous, ⇒ RbNO3, H2, Nox | Reaction with 6 M NaOH: vigorous, ⇒ H2, RbOH |
Compounds
| Oxide(s): Rb2O, Rb2O2, Rb2O3, RbO2 (rubidium superoxide) | Chloride(s): RbCl |
| Hydride(s): RbH |
Radius
| Atomic radius: 248 pm | Ionic radius (1+ ion): 166 pm |
| Ionic radius (2+ ion): pm | Ionic radius (3+ ion): pm |
| Ionic radius (2- ion): pm | Ionic radius (1- ion): pm |
Conductivity
| Thermal conductivity: 58.2 W m-1 K-1 | Electrical conductivity: 47.8 x 10-6 S m-1 |
Abundance & Isotopes
| Abundance earth's crust: 90 parts per million by weight, 21 parts per million by moles | |
| Abundance solar system: 30 parts per billion by weight, 0.4 parts per billion by moles | |
| Cost, pure: $1200 per 100g | |
| Cost, bulk: $ per 100g | |
| Source: The main ore of rubidium is lepidolite which contains 1.5% rubidium. Rubidium is usually obtained as a by product of lithium production. Rubidium metal can also be produced by reducing rubidium chloride with calcium. | |
| Isotopes: Rubidium has 29 isotopes whose half-lives are known, with mass numbers 74 to 102. Of these, one is stable: 85Rb. The isotope 87Rb which comprises almost 28% of naturally occurring rubidium is slightly radioactive, with a half-life of 49 billion years. | |
