Origins of the Names of the Periodic Table Elements - Part III

The name of this European capital city literally translates to ‘Log Islet’ in the local language. An element gets its name from the city's Latin name because it was the home town of one of its discoverers. Which element?

Holmium, after Stockholm.

This element was spectroscopically discovered by Robert Bunsen and Gustav Kirchhoff in 1860 in mineral water from Durkheim, Germany. Its identification was based upon the bright blue lines in its spectrum and it was the first element discovered by spectrum analysis. It gets its name from the Latin word meaning "sky blue" or "light blue". Which element?

Caesium

Although this element was first identified in Paris in 1886 by French chemist Paul Émile Lecoq de Boisbaudran, it was not isolated in relatively pure form until after the development of ion exchange and metallographic reduction techniques in the 1950s. Its name is derived from the Greek term for "hard to obtain". Which element?

Dysprosium

Which element, first synthesized in 1967 at the Joint Institute for Nuclear Research in Russia, gets its name from the city in which the institute is located?

Dubnium, from Dubna.

This element, discovered in 1803 by Smithson Tennant, was named after the Latin word for ‘rainbow’, because many of its salts were strongly coloured. Which element?

Iridium