Periodic Table/Rubidium
← KrSr →
37Rb85.4678 Da

Rubidium

Alkali Metal·Period 5, Group 1·s-block

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.

Gallery

Rubidium Metal Sample

Dnn87, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

Bohr model of Rubidium

Physical Propertiesmass · density · phase · crystal

Atomic Mass

85.4678Da

Density

1.5300g/cm³

Phase (STP)

Solid

Melting Point

312.4K

Boiling Point

961.1K

Molar Heat

0.3630J/(mol·K)

Crystal Structure

BCC

Lattice Constant

5.590Å

Atomic Radiiatomic · covalent · van der Waals

Atomic (Empirical)

235.00pm

Covalent

210.00pm

Van der Waals

303.00pm

Electronic Propertieselectronegativity · ionization · affinity

Electron Configuration

[Kr] 5s

Electron Shells

2, 8, 18, 8, 1

Electronegativity

0.82Pauling

Electron Affinity

0.5kJ/mol

1st Ionization Energy

4.2kJ/mol

Oxidation States

+1

Orbital DiagramAufbau · Hund's rule · Pauli exclusion

↑↓
1s2
↑↓
2s2
↑↓
↑↓
↑↓
2p6
↑↓
3s2
↑↓
↑↓
↑↓
3p6
↑↓
↑↓
↑↓
↑↓
↑↓
3d10
↑↓
4s2
↑↓
↑↓
↑↓
4p6
↑
5s1

Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s1Short: [Kr] 5s

Ionization Energies (37 known)

1st4.2 kJ/mol2nd27.3 kJ/mol3rd39.2 kJ/mol4th52.2 kJ/mol5th68.4 kJ/mol6th82.9 kJ/mol7th98.7 kJ/mol8th132.8 kJ/mol9th150.6 kJ/mol10th277.1 kJ/mol11th313.1 kJ/mol12th356.0 kJ/mol13th400.0 kJ/mol14th443.0 kJ/mol15th502.0 kJ/mol16th550.0 kJ/mol17th601.0 kJ/mol18th654.0 kJ/mol19th706.0 kJ/mol20th857.0 kJ/mol21th905.3 kJ/mol22th958.9 kJ/mol23th1024.0 kJ/mol24th1080.0 kJ/mol25th1125.0 kJ/mol26th1242.5 kJ/mol27th1294.6 kJ/mol28th3133.3 kJ/mol29th3281.0 kJ/mol30th3443.0 kJ/mol31th3600.0 kJ/mol32th3815.0 kJ/mol33th3988.0 kJ/mol34th4214.0 kJ/mol35th4356.9 kJ/mol36th18305.9 kJ/mol37th18965.5 kJ/molSuccessive Ionization Energies

Emission Spectrumvisible range · characteristic spectral lines

422
420
Rb emission
380nm750nm
780.0 nm(100%)794.8 nm(80%)421.6 nm(30%)420.2 nm(25%)

Abundanceby mass

🌍Earth's Crust
90.0 ppm
🌊Ocean
120.0 ppb
✨Universe
10.0 ppb
🧬Human Body
4.6 ppm

Log scale · ppm = parts per million by mass

Biological Role

No biological role

No known biological role. Biochemically similar to potassium; used as tracer in studies.

Discovery

Discovered By

R. Bunsen, G. Kirchoff

Named By

—

Year

1861

Nuclear Data

Known Isotopes

34

Stable Isotopes

2

Stable Mass Numbers

71, 85

Natural isotopic abundance (IUPAC recommended values)

Isotopes of Rb34 known

NuclideZNMass (AMU)Half-lifeDecayJπAbundance
71Rbstable373470.965335Stablep5/2-—
72Rb373571.958851103 nsp1+—
73Rb373672.950605Unknownβ⁺, p (1%)3/2-—
85Rbstable374884.911790Stablestable (1%)5/2-7217.0000%
87Rb375086.90918149.7 Gyβ⁻ (1%)3/2-2783.0000%
102Rb3765101.96000837.0 msβ⁻ (1%), β⁻n (0.65%), 2n4+—
103Rb3766102.96440126.0 msβ⁻ (1%), β⁻n, 2n3/2+—
104Rb3767103.970531Unknownβ⁻, β⁻n, 2n——

Click any isotope for its full page with decay chain:

71Rb72Rb73Rb74Rb75Rb76Rb77Rb78Rb79Rb80Rb81Rb82Rb83Rb84Rb85Rb86Rb87Rb88Rb89Rb90Rb91Rb92Rb93Rb94Rb95Rb96Rb97Rb98Rb99Rb100Rb101Rb102Rb103Rb104Rb
Wikipedia →Data: Bowserinator · IAEA NDS · mendeleev