Element 63 in our International Year of the Periodic Table series is europium. Europium is, appropriately, found in Euro banknotes, and also gives some of the colours in phone and TV screens.
Europium compounds are used in Euro banknotes as a security feature. The complexes used fluoresce under ultraviolet (UV) light. The UV light excites electrons in the compounds to higher energy levels (known as an excited state) before they lose this excess energy and fall back to their original position. The excess energy is lost as visible light, giving the appearance of fluorescence.
Europium compounds are also used as phosphors in CRT TVs, as well as in newer TV and phone screens, and give red and blue colours. Another application involving light sees small amounts of europium added to low-energy bulbs to give a warmer light.
Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.