Lanthanum

Lanthanum
Properties
Atomic symbol	La
Atomic number	57
Classification	Rare Earth Metals
Atomic mass	138.9055 amu
Number of Stable Isotopes	2
Density (grams per cc)	6.145 g/cm^3
Other Information
Date of discovery	1839
Name of discoverer	Carl Mosander
Name origin	From the Greek lanthanein, meaning to lie hidden.
Uses	Due to the refractive properties it adds to glass, it is used in expensive camera lenses. Also used in lighter flints, battery electrodes, catalytic converters, and as a biological tracer.
Obtained from	Found along with monazite and bastnasite.

Lanthanum is an element in the "rare earths" class of the periodic table. Specifically, it is the first in the "Lanthanide" series. It is easily oxidized in air, and reacts with water. It has two stable isotopes (actually one, but another one has a half-life of 10¹¹ years).

Lanthanum was discovered while searching for impurities in Cerium.