Cesium (Cs) - Element 55 | Properties & Electron Configuration
What is Cesium?
Cesium (Cs) is element 55, a alkali metal in period 6, group 1. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹.
| Atomic Number | 55 |
| Symbol | Cs |
| Atomic Mass | 132.91 u |
| Category | Alkali Metal |
| Period | 6 |
| Group | 1 |
| Block | s |
| Electron Configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹ |
| Short Config | [Xe] 6s¹ |
| Electronegativity | 0.79 |
| Atomic Radius | 260 pm |
| Ionization Energy | 376 kJ/mol |
| Electron Affinity | 46 kJ/mol |
| Phase (STP) | Solid |
Electron Configuration
The full electron configuration of Cesium is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹. In noble gas shorthand, this is written as [Xe] 6s¹.
Cesium is a s-block element in group 1, period 6.
Periodic Trends
Electronegativity: Cesium has a Pauling electronegativity of 0.79. Within group 1, electronegativity generally decreases down the group.
Atomic Radius: 260 pm. Across period 6, atomic radius generally decreases left to right as nuclear charge increases.
Ionization Energy: 376 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 Cesium on the Interactive Periodic TableRelated Topics
Hydrogen (H)
Properties of Hydrogen - same group as Cesium
Lithium (Li)
Properties of Lithium - same group as Cesium
Sodium (Na)
Properties of Sodium - same group as Cesium
Barium (Ba)
Properties of Barium - same period as Cesium
Lanthanum (La)
Properties of Lanthanum - same period as Cesium
Cerium (Ce)
Properties of Cerium - same period as Cesium