Cadmium compounds were formerly used as yellow pigments. Nowadays it is considered as very toxic and an environmental pollutant emitted by many industiral processes.
Name giver is Kádmos from the Greek mythology, founder of Thebes, who killed a dragon.
For a long time molybdenum was confused with lead ores. That’s why it got its name from the greek word for lead mólybdos. It is used for hardening steel. As a trace element it is essential for almost every organism. It can reach oxidation states up to six.
The Name neodymium means "new twin" (from the Greek words neo = new and didymos = twin), because it is quite similar to lanthanum. It is famous for strong magnets, which are made of an alloy of neodymium, iron and boron.
Thulium was named after the ancient mythical place called Thule, which stands for either Scandinavia or an island in the North Atlantic – depending upon interpretation.
The element cerium was named after the dwarf planet Ceres, which itself was named after the Roman goddess of agriculture and fertility. Even though it belongs to the rare earth elements, it is not so rare on earth. It is even more abundant than tin or lead – just not in its pure form but always in compounds. It is used for example in lighter flints.
The name ruthenium is derived from the Latin word Ruthenia for Russia, because it was first discovered there. As a noble metal it doesn't like to react with other elements and can rarely be found on earth.
Even though xenon is the rarest non-radioactive element on earth, it is used for many purposes, for example in xenon arc lamps, which are often found in car headlights. Its name is derived from the Greek word xénos, meaning "strange" or "foreign".
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