The classification places it in the group of rare earth elements. It was placed in the rare group elements by early researchers, not because it was rare to find from the belly of the earth, but because there were hardly any uses at that time. It is placed in the lanthanide group in the periodic table, and the symbol is Tb. It has the atomic number 65, and its atomic mass is calculated at 158.9254.
Physical & Chemical Properties
Terbium has silver-gray luster, like many metals. It is so soft that is can be cut into two with a knife. It is ductile and malleable, that is, it can be hammered into thin sheets or made into wires. Its melting point is 1,356° C or 2,473° F. The boiling point of this element is 2,800° C or 5,000° F. It is not very active like its brothers and sisters of the rare earth elements. It does not react with oxygen in the air easily, reacts slowly with water, and can dissolve readily in acids.
Terbium combines with different elements at high temperatures, like nitrogen, carbon, sulfur, phosphorous, boron, selenium, silicon, and arsenic. In the compound state, it forms binary compounds with oxidation state +3 and +2. It can form compounds like TbH2, TbH3, TbB2, Tb2S3, TbSe, TbTe and TbN and also sesquichloride Tb2Cl3.
Terbium isotopes that occur naturally are composed of 1 stable isotope, 159Tb. It has been found that, of the 33 radioisotopes 158Tb is the most stable with a half life of 180 years. Similarly, 157Tb has a half life of 71 years, and 160Tb has a half life of 72.3 days. A majority of the isotopes have a half life of less than 24 seconds, and a few have half lives of 6.907 days.
What is it Used for?
It is most commonly used as a laser material that emits coherent light at 5460Â. It is also used as a dopant for calcium fluoride, calcium tungstate, and strontium molybdate, that are used in solid state devices. It is also used as a probe in biochemistry, as it resembles calcium in behavior. It gives out fluorescence, that helps in tracking the element in biochemical experiments.
What is it Used in?
It is used in X-ray machines as well as a green phosphor activator in color television tubes. It is also used along with the element zirconium, and works as a crystal stabilizer in fuel cells that are supposed to work at high temperatures. Terbium green phosphor is used in combination with divalent europium blue phosphors and trivalent europium red phosphors. This helps in creation of 'trichromatic' lighting technology, that has a higher light output as compared to incandescent lighting. It is also used in alloys, electronic devices, and magnetomechanical devices.