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La
La at. wt. 138.91
at. no. 57
m.p. 920±5°C
b.p. 3454°C
sp. gr. 6.166 (25°C)
valence 3.
| SHELL | K | L | M | N | O | P | Q |
| SUB SHELL | He | Neon | Argon | Krypton | Xenon | Radon | Eka-radon |
| 1s | 2s 2p | 3s 3p | 3d 4s 4p | 4d 5s 5p | 4f 5d 6s 6p | 5f 6d 7s 7p | |
| Lanthanum | 1s22s22p63s23p63d104s24p64d105s25p6 | 4f05d16s2 | |||||
| Symbol | 2D3/2 | ||||||
LANTHANUM was extracted by Mosander in 1839, as a new earth, lanthana, from impure cerium nitrate, then recognized as a new element. Lanthanum is found in rarearth minerals, such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25 % and 38 %, res- pectively. Misch metal, used in making lighter flints, con- tains about 25 % lanthanum. Lanthanum was isolated in relatively pure form in 1923. Ion exchange and solvent extraction techniques have led to much easier isolation of the so-called "rare~arth" elements. The availability of lan- thanum and other rare earths has improved greatly in recent years. The metal can be produced by reducing the anhydrous fluoride with calcium. Lanthanum is silvery white, malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, and hot water attacks it much more rapidly. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. At 3100C, lanthanum changes from a hexagonal to a face-centered cubic structure, and at 8650C it again transforms into a body-centered cubic structure. Natural lanthanum is a mixture of two stable isotopes, La138 and La' 39. Seventeen other radioactive isotopes are recognized. Rare-earth compounds containing lanthanum are exten- sively used in carbon lighting applications, especially by the motion picture industry for studio lighting and projection. This application consumes about 25 % of the rare-earth compounds produced. La2O3 improved the alkali resistance of glass, and is used in making special optical glasses. Small amounts of lanthanum, as an additive, can be used to B-l8 produce nodular cast iron. Lanthanum and its compounds have a low to moderate acute toxicity rating; therefore care should be taken in handling them. The price of 99.9% La2O3 is about $8/lb. The metal costs about $70/lb.
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