Write about Terbium atom.

     

Terbium is a chemical element with the symbol Tb and atomic number 65.  It is a silvery-white, rare earth metal that is malleable, ductile, and soft enough to be cut with a knife.  The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas.  Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadlinite, monazite, xenotime, and euxentie. 

     Swedish chemist Carl Gusfaf Mosander discovered terbium as a chemical element in 1843.  He detected it as an impurity in yttrium oxide, Y2O3.  Yttrium and terbium, as well as erbium and ytterium, are named after the village of Ytterby in Sweden.  Terbium was not isolated in pure form until the advent of ion exchange techniques.

     Terbium is used ot dope calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a component of Terfenol-D( an alloy that expandes and contracts when exposed to magnetic fields more than any other alloy) terbium is of use in actuators, in naval sonar system and in sensors.