Cesium

Cesium was discovered in 1860 by the German chemist Robert Bunsen and his assistant Gustav Kirchhoff through the use of spectral analysis. They observed two bright blue lines in the spectrum of mineral water from Durkheim, Germany, which were attributed to a previously unknown element. The name 'cesium' is derived from the Latin word 'caesius,' meaning 'sky blue,' in reference to the color of the spectral lines. Despite its discovery in the 19th century, cesium's applications became more apparent with advances in technology, particularly in the field of timekeeping. In 1967, the International System of Units (SI) adopted the cesium atomic clock as the standard, defining the second based on the vibrations of cesium-133 atoms.

Cesium naturally occurs in trace amounts in the Earth's crust, primarily found in the mineral pollucite, which is its main ore. It can also be found in small quantities in other minerals such as lepidolite and zinnwaldite. The estimated abundance of cesium in the Earth's crust is about 0.00025% by weight. Due to its high reactivity and low ionization energy, cesium does not occur freely in nature but rather in various mineral forms. The largest commercial sources of cesium are found in Canada, where pollucite is mined for extraction.

While cesium's role in biological systems is not well-defined, it has been noted that cesium ions can influence cellular functions. However, cesium does not play an essential role in the biochemical processes of most organisms. High concentrations of cesium, particularly radioactive isotopes such as cesium-137, can pose health risks to living organisms, highlighting the importance of careful management regarding cesium, especially in nuclear contexts. In contrast, stable cesium forms are generally considered non-toxic at low levels, but the ecological impacts of cesium contamination can be significant.

Cesium is characterized by its soft, metallic luster and is one of the most reactive elements. It has a melting point of approximately 28.5 °C, which means it can remain liquid at room temperature, and it boils at 671 °C. Cesium has a density of 1.93 grams per cubic centimeter. The element oxidizes rapidly in air and reacts violently with water, producing cesium hydroxide and hydrogen gas. Chemically, cesium belongs to the alkali metals group, demonstrating typical properties of this group, including the formation of strong bases and the release of hydrogen when reacting with acids.

Cesium has numerous applications primarily due to its unique properties. One of the most significant uses of cesium is in atomic clocks, where cesium-133 is employed to define the second. This precision timekeeping is critical for navigation systems, telecommunications, and global positioning systems (GPS). Cesium compounds, such as cesium chloride, are also used in various industries, including ion propulsion systems and as getters in vacuum tubes. Additionally, cesium is utilized in some photoelectric cells, infrared sensors, and in the oil industry for drilling fluid formulations.

• Cesium is the only metal that is liquid at room temperature.
• The first atomic clock was built using cesium in the 1950s.
• Cesium-137 is a byproduct of nuclear fission and is used in medical applications, including cancer treatment.
• Due to its high reactivity, cesium must be stored in an inert atmosphere to prevent it from igniting spontaneously.