Element Rubidium

Rubidium ElementAn element that is an alkali metal. It has an atomic symbol Rb, atomic number 37, and atomic weight 85.47. It is used as a chemical reagent and in the manufacture of photoelectric cells.
Rubidium metal shares similarities to potassium metal and caesium metal in physical appearance, softness and conductivity. Element Rubidium cannot be stored under atmospheric oxygen, as a highly exothermic reaction will ensue, sometimes even resulting in the metal catching fire.

Names and Identifiers

Chemical Formula:Rb
Molecular Weight:85.46780 g/mol
EC Number :231-126-6
MDL Number:MFCD00134055
Color:silvery white
Other Names:Rubidij, Rubidio
PubChem CID:5357696
IUPAC Name:Rubidium
Canonical SMILES:[Rb]
ICSC Number:n/a

Physical & Chemical Properties

Density:1.532 g/cm³
Boiling Point:961 K ​(688 °C, ​1270 °F)
Melting Point:312.45 K (39.30 °C, 102.74 °F)
Molecular Formula:Rb
Flash Point:n/a
Exact Mass:84.91180
Symbol:Globally Harmonized System of ClassificationGlobally Harmonized System of Classification
Signal Word:Danger
Hazard Statements:H260-H314
Precautionary Statements:P223-P231 + P232-P280-P305 + P351 + P338-P370 + P378-P422
Hazard Codes:Xi,C,F
Risk Phrases:36/37/38-36/38-34-14/15
Safety Phrases:S26-S36/37/39-S43-S45-S36
RIDADR:UN 2031 8/PG 2
WGK Germany:3
Packaging Group:III
Hazard Class:8

Rubidium (37Rb) has 32 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (27.8%).
Normal mixes of rubidium are radioactive enough to fog photographic film in approximately 30 to 60 days.

Naturally occurring isotopes

IsotopeMass/DaNatural abundance (atom %)Nuclear spin (I)Magnetic moment (μ/μN)
85Rb84.911794 (3)72.17 (2)5/21.35303
87Rb86.909187 (3)27.83 (2)3/22.75124

Radiosotope data

IsotopeMass/DaHalf-lifeMode of decayNuclear spinNuclear magnetic moment
81Rb80.919004.57 hEC to 81Kr3/22.060
82Rb81.918211.258 mEC to 82Kr10.554508
83Rb82.9151186.2 dEC to 83Kr5/21.425
84Rb83.91438732.9 dEC to 84Kr; β to 84Sr2-1.32412
86Rb85.91117018.65 dEC to 86Kr; β to 86Sr2-1.6920
87Rb86.90918354.75 x 1010 yβ to 87Sr3/2

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