Tm Thulium 69 168.93421 6 f 69 1545.0 1950.0 [Xe] 4f13 6s2 2 8 18 31 8 2 9.32 0.000045% Silver Hexagonal 1.3 {"1":"596.7","2":"1160","3":"2285","4":"4120"} 597 50 +3,2 1.77 18.1 16.8 191.0 0.16 16.8 56.K 0 Solid, Paramagnetic, Conductor, Lanthanide, Stable, Natural THOO-li-em Soft, malleable, ductile, silvery metal Radioactive thulium is used to power portable x-ray machines, eliminating the need for electrical equipment. Found with other rare earths in the minerals gadolinite, euxenite, xenotime, and monazite. Monazite is often 50% rare earth by weight and 0.007% thulium. CQFDIZfMPVQ Thulium

Robert Bunsen and Gustav Kirchhoff were the first to suggest finding cesium in 1860 by spectrum analysis.

They discovered cesium by its two blue emission lines in a sample of Dürkheim mineral water.

The pure metal was eventually isolated by the German chemist Carl Setterberg while working on his doctorate with Kekulé and Bunsen. From the Latin word caesius, sky blue 69 1879 Per Theodore Cleve Sweden Named after "Thule", an ancient name for Scandinavia

Cesium compounds are considered to be mildly toxic

Cesium was the first element discovered using a spectroscope

The radioactive isotope cesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology.

Cesium is also used in photoelectric cells and as a catalyst in the hydrogenation of organic compounds.

Cesium vapor thermionic generators are low-power devices that convert heat energy to electrical energy.