Download Rubidium

Symbol: Rb
Atomic number: 37
Atomic mass: 85.4678
Group: Alkali Metal
Rubidium is a chemical element in the periodic table that has
the symbol Rb and atomic number 37. Rb is a soft, silverywhite metallic element of the alkali metal group
Electronic data
Thermal data
Steric Data
Shells: 2,8,18,8,1
Orbitals: [Kr] 5s1
Electronegativity: 0.9,
0.8
1. Ionization potential:
4.1771 eV
2. Ionization potential:
27.28 eV
3. Ionization potential:
40.0 eV
Oxidation states: 1
Electrical conductivity:
0.0779 10^6
Melting point: 38.89 °C
Boiling point: 686 °C
Specific heat: 0.363 J/gK
Heat of fusion: 2.192
kJ/mol
Heat of vaporization:
72.216 kJ/mol
Thermal conductivity:
0.582 W/cmK
Atomic radius: 2.98 Å
Ionic radius: 1.61 Å ()
Covalent radius: 2.16 Å
Atomic volume: 55.9 cm³/mol
Density (293 K): 1.53 g/cm³
Crystal structure: Cubic: Body centered
History
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Rubidium was discovered by
the German chemists Robert
Bunsen and Gustav Kirchoff
in 1861 while analyzing
samples of the mineral
lepidolite
(KLi2Al(Al,
Si)3O10(F, OH)2) with a
device called a spectroscope.
The sample produced a set of
deep red spectral lines they
had never seen before
Bunsen
The name rubidium (from
the Latin "rubidus" - dark
red) was coined for its bright
red spectroscopic lines.
Kirchoff
Occurrence
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This element is considered to be the 16th most abundant
element in the earth's crust.
It occurs naturally in the minerals leucite, pollucite, and
zinnwaldite, which contains traces of up to 1% of its oxide.
Lepidolite contains 1.5% rubidium and this is the commercial
source of the element.
Some potassium minerals and potassium chlorides also contain
the element in commercially significant amounts. One notable
source is also in the extensive deposits of pollucite at Bernic
Lake, Manitoba. Rubidium metal can be produced by reducing
rubidium chloride with calcium among other methods.
Isolation

Rubidium would not normally be made in the laboratory as it is
available commercially. All syntheses require an electrolytic step as
it is so difficult to add an electron to the poorly electronegative
rubidium ion Rb+.

Rubidium is not made by the same method as sodium as might
have been expected. This is because the rubidium metal, once
formed by electrolysis of liquid rubidium chloride (RbCl), is too
soluble in the molten salt.
cathode: Rb+(l) + e- Rb (l) anode: Cl-(l) 1/2Cl2 (g) + e-

Instead, it is made by the reaction of metallic sodium with hot
molten rubidium chloride.
Na + RbCl
Rb + NaCl
This is an equilibrium reaction and under these conditions the
rubidium is highly volatile and removed from the system in a form
relatively free from sodium impurities, allowing the reaction to
proceed.
Chemical reactions of the elements

Reaction of rubidium with air
If rubidium is burned in air, the result is mainly formation of
dark brown rubidium superoxide, RbO2.
Rb(s) + O2(g)
RbO2(s)

Reaction of rubidium with water
Rubidium metal reacts very rapidly with water to form a
colourless solution of rubidium hydroxide (RbOH) and
hydrogen gas (H2). The reaction is very exothermic.
2 Rb(s) + 2H2O
2RbOH(aq) + H2(g)
Chemical reactions of the elements

Reaction of rubidium with the halogens
Rubidium metal reacts vigorously with all the halogens to form
rubidium halides.
2Rb(s) + F2(g)
RbF(s)
2Rb(s) + Cl2(g)
RbCl(s)
2Rb(s) + Br2(g)
RbBr(s)
2Rb(s) + I2(g)
RbI(s)

Reaction of rubidium with acids
Rubidium metal dissolves readily in dilute sulphuric acid to form
solutions containing the aquated Rb(I) ion together with
hydrogen gas, H2.
2Rb(s) + H2SO4(aq)
2Rb+(aq) + SO42-(aq) + H2(g)
Binary Compounds
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Hydrides
HRb: rubidium (I) hydride
Fluorides
RbF: rubidium (I) fluoride
Chlorides
RbCl: rubidium (I) chloride
Bromides
RbBr: rubidium (I) bromide
Iodides
RbI: rubidium (I) iodide
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Sulfides
Rb2S: rubidium (I) sulphide
Selenides
Rb2Se: rubidium (I) selenide
Tellurides
Rb2Te: rubidium (I) telluride
Oxides
Rb2O: rubidium (I) oxide
RbO2: rubidium (I) superoxide
Rb2O2: rubidium (I) peroxide
Applications
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Rubidium is easily ionized, and so has possible use in
"ion engines" for space vehicles
As a getter in vacuum tubes.
As a photocell component.
In the making of special glasses.
Rubidium compounds are sometimes used in fireworks
to give them a purple color.