Day 55 - Cesium/Caesium
In the sixth Period and the first Group, Cesium comes from the Latin word for sky blue, due to its blue spectral lines.
Cesium was the first element ever discovered using a spectroscope.
A second has been scientifically described as the time it takes cesium to vibrate 9,129,631,770 between energy levels.
Because cesium is in the first Group, it is extremely reactive in water and must be kept under layers of oil to prevent it from exploding.
Cesium is liquid at room temperature, one of only five elements to do so.