Lanthanum

Basic Information

 * Name:** Lanthanum **Symbol:** La **Atomic Number:** 57 **Atomic Mass:** 138.9055 amu **Melting Point:** 920.0 °C (1193.15 K, 1688.0 °F) **Boiling Point:** 3469.0 °C (3742.15 K, 6276.2 °F) **Number of Protons/Electrons:** 57 **Number of Neutrons:** 82 **Classification:** Rare Earth **Crystal Structure:** Hexagonal **Density @ 293 K:** 6.7 g/cm3 **Color:** white

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0057.gif width="355" height="353"]] ||  || **Number of Energy Levels:** 6
 * First Energy Level:** **Second Energy Level:** **Third Energy Level:** **Fourth Energy Level:** **Fifth Energy Level:** **Sixth Energy Level:** ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * La-134 || 6.5 minutes ||
 * La-137 || 6000.0 years ||
 * La-138 || 1.05E10 years ||
 * La-139 || Stable ||
 * La-140 || 1.67 days ||
 * La-141 || 3.9 hours ||
 * La-142 || 1.54 minutes ||

Facts

 * Date of Discovery:** 1839 **Discoverer:** Carl Mosander **Name Origin:** From the Greek word //lanthaneis// (to lie hidden) **Uses:** expensive camera lenses **Obtained From:** monazite, bastnasite

It is found in some rare-earth materials, usually in combination with cerium and other rare earth elements. Lanthanum is a malleable, ductile, and soft metal that oxidizes rapidly when exposed to air. It is produced from the minerals monazite and bastnasite using a complex multistage extraction process. Lanthanum compounds have numerous applications as catalysts, additives in glass, carbon lighting for studio lighting and projection, ignition elements in lighters and torches, electron cathodes, scintillators and others.

Physical properties
Lanthanum is a soft, malleable, silvery white metal which has [|hexagonal] crystal structure at room temperature. At 310 °C, lanthanum changes to a [|face-centered cubic] structure, and at 865 °C into a [|body-centered cubic] structure. [|[2]] Lanthanum easily is oxidized (a centimeter-sized sample will completely oxidize within a year) [|[3]] and is therefore used as in elemental form only for research purposes. For example, single La atoms have been isolated by implanting them into [|fullerene] molecules. [|[4]] If [|carbon nanotubes] are filled with those lanthanum-encapsulated fullerenes and annealed, metallic nanochains of lanthanum are produced inside carbon nanotubes. [|[5]]



Chemical properties
Lanthanum exhibits two oxidation states, +3 and +2, the former being much more stable. For example, LaH3 is more stable than LaH2. [|[6]] Lanthanum burns readily at 150 [|°C] to form [|lanthanum(III) oxide] : 4 La + 3 O2 → 2 La2O3 However, when exposed to moist air at room temperature, lanthanum oxide forms a hydrated oxide with a large volume increase. [|[6]] Lanthanum is quite [|electropositive] and reacts slowly with cold water and quite quickly with hot water to form lanthanum hydroxide: 2 La (s) + 6 H2O (l) → 2 La(OH)3 (aq) + 3 H2 (g) Lanthanum metal reacts with all the halogens. The reaction is vigorous if conducted at above 200 °C: 2 La (s) + 3 F2 (g) → 2 LaF3 (s)2 La (s) + 3 Cl2 (g) → 2 LaCl3 (s)2 La (s) + 3 Br2 (g) → 2 LaBr3 (s)2 La (s) + 3 I2 (g) → 2 LaI3 (s) Lanthanum dissolves readily in dilute [|sulfuric acid] to form solutions containing the La(III) ions, which exist as [La(OH2)9]3+ complexes: [|[7]] 2 La(s) + 3 H2SO4 (aq) → 2 La3+(aq) + 3 SO 2− 4 (aq) + 3 H2 (g) Lanthanum combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic at elevated temperatures, forming binary compounds. [|[6]] The electron configuration for Ln is [Xe] 4f0, and the ion is colourless. The ground state term symbol is 1I0 [|[8]].

Isotopes
Naturally occurring lanthanum is composed of one stable (139La) and one [|radioactive] (138La) [|isotope], with the stable isotope, 139La, being the most abundant (99.91% [|natural abundance] ). 38 [|radioisotopes] have been characterized with the most stable being 138La with a [|half-life] of 1.05×1011 years, and 137La with a half-life of 60,000 years. Most of the remaining radioactive isotopes have half-lives that are less than 24 hours, and the majority of these have half-lives less than 1 minute. This element also has three [|meta states]. The isotopes of lanthanum range in [|atomic weight] from 117 [|u] (117La) to 155 u (155La).