Lanthanum Information
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Lanthanum Element
Lanthanum is a chemical element
with the symbol La and atomic number 57. It is a soft, ductile, silvery-white
metal that tarnishes slowly when exposed to air and is soft enough to be cut
with a knife. It is the eponym of the lanthanide series, a group of 15 similar
elements between lanthanum and lutetium in the periodic table, of which
lanthanum is the first and the prototype. It is also sometimes considered the
first element of the 6th-period transition metals, which would put it in group
3, although lutetium is sometimes placed in this position instead. Lanthanum is
traditionally counted among the rare earth elements. The usual oxidation state
is +3. Lanthanum has no biological role in humans but is essential to some
bacteria. It is not particularly toxic to humans but does show some
antimicrobial activity
Lanthanum is a ductile and
malleable silvery white metal that is soft enough to be cut with a knife. It is
the second most reactive of the rare-earth metals after europium. Lanthanum
oxidizes in air at room temperature to form La2O3. It slowly reacts with water
and quickly dissolves in diluted acids, except hydrofluoric acid (HF) because
of formation of a protective fluoride (LaF3) layer on the surface of the metal.
The metal is paramagnetic from 6 K (−267 °C, or −449 °F) to its melting point
at 1,191 K (918 °C, or 1,684 °F) with a nearly temperature-independent magnetic
susceptibility between 4 and 300 K (−269 and 27 °C, or −452 and 80 °F).
Lanthanum becomes superconducting at atmospheric pressure below 6.0 K (−267.2
°C, or −448.9 °F) in the face-centred cubic β-phase or 5.1 K (−268.1 °C, or
−450.5 °F) in the double close-packed hexagonal α-phase.
Lanthanum usually occurs
together with cerium and the other rare earth elements. Lanthanum was first
found by the Swedish chemist Carl Gustaf 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.[5] It
is extracted from those minerals by a process of such complexity that pure
lanthanum metal was not isolated until 1923.
Lanthanum compounds have
numerous applications as catalysts, additives in glass, carbon arc lamps for
studio lights and projectors, ignition elements in lighters and torches,
electron cathodes, scintillators, GTAW electrodes, and other things. Lanthanum
carbonate is used as a phosphate binder in cases of high levels of phosphate in
the blood seen with kidney failure.
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