Eka (chemistry)
The prefix Eka (from Sanskrit एक eka "one") was used to denote chemical elements not yet discovered in the periodic table .
A searched element was provisionally given the name of an already known element together with the prefix Eka if it was a period below the known element. The Russian chemist Dmitri Mendeleev predicted the existence of three elements in 1871 because they would fill corresponding gaps in his periodic table. For this reason he introduced the prefix Eka and named the three elements he postulated according to this principle. He was referring to the division into periods in his short periodic table published in 1871 :
- Eka-Aluminum was discovered by Paul Émile Lecoq de Boisbaudran in 1875 and named Gallium after his home country France (Latin Gallia ) . The gap to be filled can be found with the entry "- = 68" in group III and row 5 of the short-period system below the aluminum (see figure). Even in today's form of the periodic table, gallium is a period under aluminum.
- Eka-Bor was discovered by Lars Fredrik Nilson in 1879 and named Scandium after his native Scandinavia . The gap to be filled can be found with the entry “- = 44” in group III and row 4 of the short period table below the boron. In today's form of the periodic table, aluminum is instead under boron.
- Eka-Silicium was discovered by Clemens Winkler in 1886 and named germanium after his home country Germany (lat. Germania ) . The gap to be filled can be found with the entry “- = 72” in group IV and row 5 of the short-period system below the silicon. Even in today's form of the periodic table, germanium is one period below silicon.
Later, the name was based on the period division of the modern periodic table. Today, instead of the prefixes Eka and Dwi, systematic element names according to the atomic number are used for elements that have not yet been named.