Cesium
⏰ In Your World
Cesium is the king of precision. The international definition of a second is based on the vibrations of a cesium-133 atom. This makes it the heart of atomic clocks, the most accurate timekeeping devices in the world, which are essential for GPS, the internet, and cell phone networks. Cesium is also one of the most reactive metals; it has a low melting point and will explode on contact with water.
📖 The Discovery Story
Cesium was discovered in 1860 by German scientists Robert Bunsen and Gustav Kirchhoff using their newly invented spectroscope. While analyzing mineral water from Dürkheim, Germany, they observed two bright blue lines in the spectrum that did not match any known element. They named the new element "cesium" from the Latin word caesius, meaning "sky-blue," in honor of its distinctive spectral lines.
📊 Properties at a Glance
| Phase at STP | Solid |
| Melting Point | 28.5 °C / 83.3 °F |
| Boiling Point | 671 °C / 1240 °F |
| Electron Configuration | [Xe] 6s¹ |
| Abundance in Earth's Crust | 0.0003% |
⚠️ Safety & Handling
Cesium is the most reactive of the stable alkali metals. It is pyrophoric, meaning it ignites spontaneously in air, and it reacts explosively with water, even cold water. It must be stored in sealed glass ampoules under a vacuum or an inert atmosphere. The radioactive isotope Cesium-137 is a dangerous fission product from nuclear reactors.