Rubidium

Rubidium (Rb)

Soft silvery metallic element, belongs to group 1 of the periodic table. Rb-97, the naturally occurring isotope, is radioactive. It is highly reactive, with properties similar to other elements in group 1, like igniting spontaneously in air. Discovered spectroscopically in 1861 by W. Bunsen and G.R. Kirchoff.
Atomic Number37
Atomic Weight85.4678
Mass Number85
Group1
Period5
Blocks
Protons37 p+
Neutrons48 n0
Electrons37 e-
RbMetal.JPG Animated Bohr Model of Rb (Rubidium) Enhanced Bohr Model of Rb (Rubidium) Bohr Model: Rb (Rubidium) Orbital Diagram of Rb (Rubidium)

Properties

Atomic Radius
235 pm
Molar Volume
Covalent Radius
210 pm
Metallic Radius
216 pm
Ionic Radius
152 pm
Crystal Radius
166 pm
Van der Waals Radius
303 pm
Density
1.53 g/cm³
Energy
Proton Affinity
Electron Affinity
0.48592 eV/particle
Ionization Energy
4.177128 eV/particle
Heat of Vaporization
75.8 kJ/mol
Heat of Fusion
2.2 kJ/mol
Heat of Formation
80.9 kJ/mol
Electrons
Electron Shells2, 8, 18, 8, 1
Valence Electrons1
Electron Configuration[Kr] 5s1
Oxidation States-1, 1
Electronegativity
0.82
Electrophilicity
0.7363448717297969 eV/particle
Phases
PhaseSolid
Gas Phase
Boiling Point
961.15 K
Melting Point
312.45 K
Critical Pressure
16 MPa
Critical Temperature
2,093.15 K
Triple Point
312.41 K
Visual
Color
Silver
Appearancegrey white
Refractive Index
Thermodynamic Properties
Thermal Conductivity
58.2 W/(m K)
Thermal Expansion
Molar Heat Capacity
31.06 J/(mol K)
Specific Heat Capacity
0.363 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
TypeConductor
Electrical Conductivity
8.3 MS/m
Electrical Resistivity
0.00000012 m Ω
Superconducting Point
Magnetism
Typeparamagnetic
Magnetic Susceptibility (Mass)
0.0000000026 m³/Kg
Magnetic Susceptibility (Molar)
0.000000000222 m³/mol
Magnetic Susceptibility (Volume)
0.00000398
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal StructureBody Centered Cubic (BCC)
Lattice Constant
5.59 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties
Hardness
0.3 MPa
Bulk Modulus
2.5 GPa
Shear Modulus
Young Modulus
2.4 GPa
Poisson Ratio
Speed of Sound
1,300 m/s
Classification
CategoryAlkali metals, Alkali metals
CAS GroupIA
IUPAC GroupIA
Glawe Number9
Mendeleev Number4
Pettifor Number9
Geochemical Classalkali metal
Goldschmidt Classlitophile
Other
Gas Basicity
Dipole Polarizability
319.8 ± 0.3 a₀
C6 Dispersion Coefficient
4,769 a₀
Allotropes
Neutron Cross Section
0.38
Neutron Mass Absorption
0.0003
Quantum Numbers2S1/2
Space Group229 (Im_3m)

Isotopes of Rubidium

Stable Isotopes2
Unstable Isotopes32
Radioactive Isotopes32

71Rb

Abundance
Relative Atomic Mass
70.965335 ± 0.000429 Da
Mass Number71
G-Factor
Half Life
Spin5/2
Quadrupole Moment
Discovery Year
Parity-

71Rb Decay Modes
Decay ModeIntensity
p (proton emission)%

72Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
71.958851 ± 0.000537 Da
Mass Number72
G-Factor
Half Life
103 ± 22 ns
Spin1
Quadrupole Moment
Discovery Year2017
Parity+

72Rb Decay Modes
Decay ModeIntensity
p (proton emission)%

73Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
72.950604506 ± 0.000043794 Da
Mass Number73
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year1996
Parity-

73Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)%
p (proton emission)100%

74Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
73.944265867 ± 0.000003249 Da
Mass Number74
G-Factor
0
Half Life
64.78 ± 0.03 ms
Spin0
Quadrupole Moment
0
Discovery Year1977
Parity+

74Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)%

75Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
74.9385732 ± 0.000001266 Da
Mass Number75
G-Factor
0.386 ± 0.00066666666666667
Half Life
19 ± 1.2 s
Spin3/2
Quadrupole Moment
0.81 ± 0.04
Discovery Year1975
Parity-

75Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

76Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
75.935073031 ± 0.000001006 Da
Mass Number76
G-Factor
-0.372552 ± 0.000011
Half Life
36.5 ± 0.6 s
Spin1
Quadrupole Moment
0.41 ± 0.09
Discovery Year1969
Parity-

76Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+α (β+-delayed α emission)3.8%

77Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
76.930401599 ± 0.0000014 Da
Mass Number77
G-Factor
0.43622666666667 ± 0.000013333333333333
Half Life
3.78 ± 0.04 m
Spin3/2
Quadrupole Moment
0.84 ± 0.17
Discovery Year1972
Parity-

77Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

78Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
77.928141866 ± 0.000003475 Da
Mass Number78
G-Factor
0
Half Life
17.66 ± 0.03 m
Spin0
Quadrupole Moment
0
Discovery Year1968
Parity+

78Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

79Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
78.923990095 ± 0.000002085 Da
Mass Number79
G-Factor
1.34292 ± 0.00048
Half Life
22.9 ± 0.5 m
Spin5/2
Quadrupole Moment
-0.12 ± 0.04
Discovery Year1957
Parity+

79Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

80Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
79.922516442 ± 0.000002 Da
Mass Number80
G-Factor
-0.0833 ± 0.0007
Half Life
33.4 ± 0.7 s
Spin1
Quadrupole Moment
0.42 ± 0.08
Discovery Year1961
Parity+

80Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

81Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
80.9189939 ± 0.000005265 Da
Mass Number81
G-Factor
1.3727333333333 ± 0.00093333333333333
Half Life
4.572 ± 0.004 h
Spin3/2
Quadrupole Moment
0.48 ± 0.1
Discovery Year1949
Parity-

81Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

82Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
81.918209023 ± 0.00000323 Da
Mass Number82
G-Factor
0.554403 ± 0.000016
Half Life
1.2575 ± 0.0002 m
Spin1
Quadrupole Moment
0.23 ± 0.1
Discovery Year1949
Parity+

82Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

83Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
82.915114181 ± 0.0000025 Da
Mass Number83
G-Factor
0.56984 ± 0.00032
Half Life
86.2 ± 0.1 d
Spin5/2
Quadrupole Moment
0.24 ± 0.05
Discovery Year1950
Parity-

83Rb Decay Modes
Decay ModeIntensity
ϵ (electron capture)100%

84Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
83.914375223 ± 0.000002355 Da
Mass Number84
G-Factor
-0.6625 ± 0.001
Half Life
32.82 ± 0.07 d
Spin2
Quadrupole Moment
-0.02 ± 0.04
Discovery Year1947
Parity-

84Rb Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)96.1%
β (β decay)3.9%

85Rb

Abundance
72.17 ± 0.02
Relative Atomic Mass
84.91178973604 ± 0.00000000537 Da
Mass Number85
G-Factor
0.541224 ± 0.000016
Half Life
Spin5/2
Quadrupole Moment
0.276 ± 0.001
Discovery Year1921
Parity-

86Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
85.911167443 ± 0.000000214 Da
Mass Number86
G-Factor
-0.8487 ± 0.0008
Half Life
18.645 ± 0.008 d
Spin2
Quadrupole Moment
0.23 ± 0.06
Discovery Year1941
Parity-

86Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
ϵ (electron capture)0.0052%

87Rb

AbundanceRadioactive ☢️
27.83 ± 0.02
Relative Atomic Mass
86.909180529 ± 0.000000006 Da
Mass Number87
G-Factor
1.8341933333333 ± 0.000053333333333333
Half Life
49.7 ± 0.3 Gy
Spin3/2
Quadrupole Moment
0.1335 ± 0.0005
Discovery Year1921
Parity-

87Rb Decay Modes
Decay ModeIntensity
β (β decay)100%

88Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
87.91131559 ± 0.00000017 Da
Mass Number88
G-Factor
0.253755 ± 0.00001
Half Life
17.78 ± 0.03 m
Spin2
Quadrupole Moment
-0.01 ± 0.11
Discovery Year1939
Parity-

88Rb Decay Modes
Decay ModeIntensity
β (β decay)100%

89Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
88.912278136 ± 0.000005825 Da
Mass Number89
G-Factor
1.5887333333333 ± 0.00046666666666667
Half Life
15.32 ± 0.1 m
Spin3/2
Quadrupole Moment
0.17 ± 0.03
Discovery Year1940
Parity-

89Rb Decay Modes
Decay ModeIntensity
β (β decay)100%

90Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
89.914797557 ± 0.000006926 Da
Mass Number90
G-Factor
0
Half Life
158 ± 5 s
Spin0
Quadrupole Moment
0
Discovery Year1951
Parity-

90Rb Decay Modes
Decay ModeIntensity
β (β decay)100%

91Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
90.916537261 ± 0.000008375 Da
Mass Number91
G-Factor
1.4540666666667 ± 0.001
Half Life
58.2 ± 0.3 s
Spin3/2
Quadrupole Moment
0.19 ± 0.05
Discovery Year1951
Parity-

91Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

92Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
91.919728477 ± 0.000006573 Da
Mass Number92
G-Factor
0
Half Life
4.48 ± 0.03 s
Spin0
Quadrupole Moment
0
Discovery Year1960
Parity-

92Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)0.0107%

93Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
92.922039334 ± 0.000008406 Da
Mass Number93
G-Factor
0.56368 ± 0.00064
Half Life
5.84 ± 0.02 s
Spin5/2
Quadrupole Moment
0.21 ± 0.06
Discovery Year1960
Parity-

93Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)1.39%

94Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
93.926394819 ± 0.000002177 Da
Mass Number94
G-Factor
0.49936666666667 ± 0.0006
Half Life
2.702 ± 0.005 s
Spin3
Quadrupole Moment
0.2 ± 0.07
Discovery Year1961
Parity-

94Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)10.3%

95Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
94.929263849 ± 0.000021733 Da
Mass Number95
G-Factor
0.5332 ± 0.0012
Half Life
377.7 ± 0.8 ms
Spin5/2
Quadrupole Moment
0.26 ± 0.09
Discovery Year1967
Parity-

95Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)8.7%

96Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
95.934133398 ± 0.000003599 Da
Mass Number96
G-Factor
0.73275 ± 0.00085
Half Life
201.5 ± 0.9 ms
Spin2
Quadrupole Moment
0.3 ± 0.09
Discovery Year1967
Parity-

96Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)13.7%
2n (2-neutron emission)%

97Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
96.937177117 ± 0.000002052 Da
Mass Number97
G-Factor
1.2266666666667 ± 0.0013333333333333
Half Life
169.1 ± 0.6 ms
Spin3/2
Quadrupole Moment
0.7
Discovery Year1969
Parity+

97Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)25.5%
2n (2-neutron emission)%

98Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
97.941632317 ± 0.000017265 Da
Mass Number98
G-Factor
0
Half Life
115 ± 6 ms
Spin0
Quadrupole Moment
0
Discovery Year1971
Parity-

98Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)14.3%
2n (2-neutron emission)0.054%

99Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
98.94511919 ± 0.000004327 Da
Mass Number99
G-Factor
Half Life
54 ± 4 ms
Spin3/2
Quadrupole Moment
Discovery Year1971
Parity+

99Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)17.3%
2n (2-neutron emission)%

100Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
99.950331532 ± 0.000014089 Da
Mass Number100
G-Factor
Half Life
51.3 ± 1.6 ms
Spin4
Quadrupole Moment
Discovery Year1978
Parity-

100Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)5.6%
2n (2-neutron emission)0.15%

101Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
100.954302 ± 0.000022 Da
Mass Number101
G-Factor
Half Life
31.8 ± 3.3 ms
Spin3/2
Quadrupole Moment
Discovery Year1992
Parity+

101Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)28%
2n (2-neutron emission)%

102Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
101.960008 ± 0.000089 Da
Mass Number102
G-Factor
Half Life
37 ± 4 ms
Spin4
Quadrupole Moment
Discovery Year1995
Parity+

102Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)65%
2n (2-neutron emission)%

103Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
102.964401 ± 0.000429 Da
Mass Number103
G-Factor
Half Life
26 ± 11 ms
Spin3/2
Quadrupole Moment
Discovery Year2010
Parity+

103Rb Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

104Rb

AbundanceRadioactive ☢️
Relative Atomic Mass
103.970531 ± 0.000537 Da
Mass Number104
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year2018
Parity

104Rb Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

History

German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 by the newly developed method of flame spectroscopy. The separation of the metal was tried by Bunsen, but he never got samples with more than 18% of Rubidium. The separation of the metal was only accomplished by George de Hevesy, through the hydrolysis of melted rubidium hydroxide. From the Latin word rubidus, deepest red

DiscoverersR. Bunsen, G. Kirchoff
Discovery LocationGermany
Discovery Year1861
Etymology (Name Origin)Latin: rubidus (deep red); the color its salts impart to flames.
Pronunciationroo-BID-i-em (English)
Rubidium is not known to be toxic
Rubidium burns with a reddish-violet flame color

Uses

Rubidium is used as a getter in vacuum tubes and as a photocell component. Rubidium compounds are sometimes used in fireworks to give them a purple color. Rubidium salts are used in glasses and ceramics. Rubidium-87 is slightly radioactive and has been used extensively in dating rocks. Used as a catalyst, photocells, and vacuum and cathode-ray tubes.

Sources

Occurs abundantly, but so widespread that production is limited. Usually obtained from lithium production.

Abundance
Abundance in Earth's crust
Abundance in Oceans
0.12 mg/L
Abundance in Human Body
0.00046 %
Abundance in Meteor
0.00032 %
Abundance in Sun
0.000003 %
Abundance in Universe
0.000001 %

Nuclear Screening Constants

1s0.7922
2p3.9612
2s9.8432
3d15.3208
3p15.6967
3s15.1573
4p26.1192
4s24.612
5s32.0155