Stable isotope Rubidium (Rb)

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Rb-85 37 48 84.911792 72.16% ≥99.50% Chloride
Rb-87 37 50 86.909186 27.84% >98.00% Chloride
Rb-87 37 50 86.909186 27.84% >98.00% Metal

Properties of Rubidium

Name Rubidium
Symbol Rb
Atomic number 37
Atomic weight 85.468
Standard state Solid at 298 °K
CAS Registry ID 7440-17-7
Group in periodic table 1
Group name Alkali metal
Period in periodic table 5
Block in periodic table s-block
Color Silvery white
Classification Metallic
Melting point 39.3 °C
Boiling point 686 °C
Vaporization point 689 °C
Thermal conductivity 58.2 W/(m·K) at 298.2 °K
Electrical resistivity 12.5 µΩ·cm at 20 °C
Electronegativity 0.8
Specific heat 0.36 kJ/kg K
Heat of vaporization 72 kJ·mol-1
Heat of fusion 2.19 kJ·mol-1
Density of liquid 1.47 g/cm3 at 39.3 °C
Density of solid 1.53 g/cm3
Electron configuration [Kr]5s1
Atomic radius 2.43 Å
Ionic radius Rb+: 1.48 Å
Atomic volume 55.9 cm3/g-atom at 20 ºC
Ionization potential 4.177 V
Oxidation state +1
Mohs hardness scale 0.3