Rubidium (Rb) - Element 37 | Properties & Electron Configuration

What is Rubidium?

Rubidium (Rb) is element 37, a alkali metal in period 5, group 1. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹.

Atomic Number37
SymbolRb
Atomic Mass85.468 u
CategoryAlkali Metal
Period5
Group1
Blocks
Electron Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹
Short Config[Kr] 5s¹
Electronegativity0.82
Atomic Radius235 pm
Ionization Energy403 kJ/mol
Electron Affinity47 kJ/mol
Phase (STP)Solid

Electron Configuration

The full electron configuration of Rubidium is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹. In noble gas shorthand, this is written as [Kr] 5s¹.

Rubidium is a s-block element in group 1, period 5.

Periodic Trends

Electronegativity: Rubidium has a Pauling electronegativity of 0.82. Within group 1, electronegativity generally decreases down the group.

Atomic Radius: 235 pm. Across period 5, atomic radius generally decreases left to right as nuclear charge increases.

Ionization Energy: 403 kJ/mol. Ionization energy generally increases across a period and decreases down a group.

View all 118 elements with trend overlays for electronegativity, atomic radius, ionization energy, and electron affinity.

Explore Rubidium on the Interactive Periodic Table

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