Lanthanum ground state electronic configuration

Elemental lanthanum has a ground state (electronic configuration) of [Xe]5d6s. Naturally occurring lanthanum is a mixture of two stable isotopes, La and La. The element was discovered in 1839 by Carl Gustaf Mosander in the form of the lanthanum oxide, at that time called lanthana. The name is derived from the Greek lanthanein ( to fie hidden ), as the element had been overlooked due to its similarity to the earlier discovered cerium. 

The formation and properties of the lanthanide complex species can be best understood by summarizing first some of the pertinent general characteristics of these elements. In their ground states, the lanthanide atoms have the characteristic valence-shell electronic configurations 4/"5 d 6 or 4 / + 6 where n = 0 for lanthanum and 14 for lutetium, overlying the closed-shell xenon arrangement. The atoms are large and readily oxidized. In both aqueous or nonaqueous systems and the solid state, oxidation... 

Hund 22) described the relations between atomic spectroscopy and the Periodic Table. This was a most important pioneer work but made one uncertain extrapolation the almost invariant trivalency made it highly probable that the groundstate of the neutral atoms from lanthanum to lutetium belong to the electron configuration [Xe] 4fcore electrons. We write [68] for the closed shells [Xe] 4fi which are the ground states of Yb+2, Lu+3, Hf+ , . .. 

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