Terbium is a silvery-white element, which is malleable and so soft that it can be cut with a knife.
It is named after the Swedish village of Ytterby, where the first sample of the element was found.
In 1843, Swedish chemist Carl Gustaf Mosander separated the mineral gadolinite into three materials, which he called yttria, erbia and terbia. From two of these substances, he discovered erbium and terbium. Erbium and two other elements namely ytterbium and yttrium are also named after Ytterby. Although terbium is relatively stable in the air, it reacts with water when exposed to it. It’s used in x-ray imaging screens and CDs. Terbium has the atomic number 65, and is represented as Tb.
Dysprosium is a soft silvery metal. The element was discovered in 1886 by Paul-Emile Lecoq de Boisbaudran, a French chemist, but he was not able to isolate it. It was not isolated until 1950, when Canadian scientist Frank Spedding and his team developed ion-exchange separation and metallographic reduction techniques.
Dysprosium is not currently used for a wide range of applications except when there is no other alternative. The atomic number of dysprosium is 66, and the symbol is Dy.
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