Atomic symbol: Cs
Atomic number: 55
Atomic mass: 132.91
Appearance: Soft, silvery-golden solid at 25°C
Series: Alkali metals
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹
Low melting point of only 28.5°C means it is near liquid at room temperature, a property only shared with 3 other elements. Apart from mercury, at 641°C, cesium has the lowest of all metals.
Very soft, ductile, and extremely reactive and hazardous.
Fun Fact! Cesium is the first element to be discovered via emission spectroscopy.