Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Lantan — element pobochnoy podgruppy tret'ey gruppy shestogo perioda periodicheskoy sistemy khimicheskikh elementov D. I. Mendeleeva, atomnyy nomer 57. Oboznachaetsya simvolom La (lat. Lanthanum). Prostoe veshchestvo lantan (CAS-nomer: 7439-91-0) — metall serebristo-belogo tsveta. Sushchestvuet v tryekh kristallicheskikh modifikatsiyakh: α-La s geksagonal'noy reshyetkoy, β-La s kubicheskoy reshyetkoy tipa medi, γ-La s kubicheskoy ob"yemnotsentrirovannoy reshyetkoy tipa α-Fe, temperatury perekhodov α↔β 277 °C i β↔γ 861 °C. Lantan, kak khimicheskiy element, ne udavalos' otkryt' na protyazhenii 36 let. V 1803 g. 24-letniy shvedskiy khimik Yyens Yakob Bertselius issledoval mineral, izvestnyy teper' pod nazvaniem tserita. V etom minerale byla obnaruzhena ittrievaya zemlya i eshche odna redkaya zemlya, ochen' pokhozhaya na ittrievuyu. Ee nazvali tserievoy. V 1826 g. Karl Mozander issledoval tserievuyu zemlyu i zaklyuchil, chto ona neodnorodna, chto v ney, pomimo tseriya, soderzhitsya eshche odin novyy element. Dokazat' slozhnost' tserievoy zemli Mozanderu udalos' lish' v 1839 g. On sumel vydelit' novyy element, kogda v ego rasporyazhenii okazalos' bol'shee kolichestvo tserita.