found: Emsley, J. Nature's building blocks, 2011(Scandium; Sc. When Dimitri Mendeleyev devised his periodic table of the elements in 1869 he noticed that there was a gap in atomic weights between calcium (40) and titanium (48) and he predicted that there should be another element of intermediate atomic weight (44) which he referred to as eka-boron, since he thought it would come below boron in the same group III of his table. Scandium was discovered 10 years later. This was the missing eka-boron predicted by Mendeleyev; scandium is a soft, silvery, yellow-white metal and a member of group 3 of the periodic table)
