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Cerium content in the soil varies between 2 and 150 ppm, with an average of 50 ppm; seawater contains 1.5 parts per trillion of cerium. [38] Cerium occurs in various minerals, but the most important commercial sources are the minerals of the monazite and bastnäsite groups, where it makes up about half of the lanthanide content.
Color code: carbon, C, blue-gray; fluorine, F, green; cerium, Ce, white; oxygen, O, red. Bastnäsite is closely related to the mineral series parisite. [7] The two are both rare-earth fluorocarbonates, but parisite's formula of Ca(Ce, La, Nd) 2 (CO 3) 3 F 2 contains calcium (and a small amount of neodymium) and a
Samarium is not absorbed by plants to a measurable concentration and so is normally not part of human diet. However, a few plants and vegetables may contain up to 1 part per million of samarium. Insoluble salts of samarium are non-toxic and the soluble ones are only slightly toxic.
Samarium-149 is the second most important neutron poison in nuclear reactor physics. Samarium-151, produced at lower yields, is the third most abundant medium-lived fission product but emits only weak beta radiation. Both have high neutron absorption cross sections, so that much of them produced in a reactor are later destroyed there by neutron ...
It contains both 7-coordinate and 8-coordinate cerium ions, Ce 3+, with monocapped and bicapped trigonal prismatic coordination geometry, respectively. The sulfide ions, S 2−, are 5-coordinate. [5] Two thirds of them adopt a square pyramidal geometry and one third adopt a trigonal bipyramidal geometry. [6]
The rare earth element neodymium is found in monazite, making it a rare mineral. [25] Moreover, monazite contains many other rare metals such as cerium, lanthanum, praseodymium, and samarium, making it a critical source of renewable energy. [26] Recycled magnets can also be derived from these minerals due to the metals they contain. [25]
Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm 2 O 3 with samarium metal at high temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure.
There are two kinds of samarium coordination in the solid, one is eight coordinated with sulfur surrounding in a bicapped trigonal pyramid. The other is a sevenfold capped distorted octahedral arrangement. This structure is similar to other light rare-earth element sulfides. [2] Samarium(III) sulfide is a semiconductor with a band gap of 1.7 eV ...