Eka

Eka is a prefix for a chemical element which is listed in the periodic table under another element.

The prefix eka- was used especially to name as yet undiscovered elements.For example germanium was called ekasilicon until its discovery.The prefix originates from the Sanskrit word "eka" meaning "one" and was coined by Dmitri Mendeleev.The prefixes di- and tri- from the Latin prefixes meaning "two" and "three" respectively, have been used for undiscovered elements two or three places in the periodic table below the element providing the base name.Current official IUPAC practice is to use a systematic element name based on the atomic number of the element as the provisional name, instead of being based on its position in the periodic table as these prefixes require.

It has been speculated that the similarity between the tabular structure commonly used to present the Sanskrit abugida and the periodic table is what led to Mendeleev choosing to use Sanskrit as the basis of these prefixes.

Sometimes the eka- prefix is used to refer to some transuranic elements, for example eka-lead for ununquadium and eka-radon for ununoctium.