Rubidium

Chaitra 26/06/2026 19:58:08 Updated 26/06/2026 19:58:08

Property	Value
Atomic Number	37
Element	Rubidium
Symbol	Rb
Atomic Mass	85.468 u
Number of Neutrons	48 (most common isotope, Rubidium-85)
Number of Protons	37
Number of Electrons	37
Period	5
Group	1
Phase	Solid
Radioactive	No (contains naturally occurring radioactive isotope Rb-87)
Natural	Yes
Metal	Yes
Nonmetal	No
Metalloid	No
Type	Alkali Metal
Atomic Radius	265 pm
Electronegativity	0.82 (Pauling scale)
First Ionization Energy	4.177 eV
Density	1.532 g/cm³
Melting Point	39.31 °C
Boiling Point	688 °C
Number of Isotopes	2 naturally occurring (Rb-85, Rb-87)
Discoverer	Robert Bunsen, Gustav Kirchhoff
Year	1861
Specific Heat	0.363 J/g·K
Number of Shells	5
Number of Valence Electrons	1