What is lanthanum named for?
Lanthanum
Lanthanum usually occurs together with cerium and the other rare earth elements. Lanthanum was first found by the Swedish chemist Carl Gustav Mosander in 1839 as an impurity in cerium nitrate – hence the name "lanthanum", from the Ancient Greek "λανθάνειν" ("lanthanein"), meaning "to lie hidden". Although it is classified as a rare earth element, lanthanum is the 28th most abundant element in the Earth's crust, almost three times as abundant as lead. In minerals such as monazite and bastnäsite, lanthanum composes about a quarter of the lanthanide content. It is extracted from those minerals by a process of such complexity that pure lanthanum metal was not isolated until 1923.
Group 3 element
Three group 3 elements occur naturally: scandium, yttrium, and either lanthanum or lutetium. Lanthanum continues the trend started by two lighter members in general chemical behavior, while lutetium behaves more similarly to yttrium. While the choice of lutetium would be in accordance with the trend for period 6 transition metals to behave more similarly to their upper periodic table neighbors, the choice of lanthanum is in accordance with the trends in the s-block, which the group 3 elements are chemically more similar to. They all are silvery-white metals under standard conditions. The fourth element, either actinium or lawrencium, has only radioactive isotopes. Actinium, which occurs only in trace amounts, continues the trend in chemical behavior for metals that form tripositive ions with a noble gas configuration; synthetic lawrencium is calculated and partially shown to be more similar to lutetium and yttrium. So far, no experiments have been conducted to synthesize any element that could be the next group 3 element. Unbiunium (Ubu), which could be considered a group 3 element if preceded by lanthanum and actinium, might be synthesized in the near future, it being only three spaces away from the current heaviest element known, oganesson.