Main physicochemical properties of rare earth elements

Rare earth elements are typical metal elements. Their metal activity is next only to alkali metal and alkaline earth metal, but more active than other metal elements. Among the 17 rare earth elements, according to the active order of metals, scandium, yttrium and lanthanum increase, while lanthanum decreases from lanthanum to lutetium, that is, lanthanum is the most active. Rare earth elements can form chemically stable oxides, halides and sulfides. Rare earth elements can react with nitrogen, hydrogen, carbon and phosphorus, and are easily soluble in hydrochloric acid, sulfuric acid and nitric acid.
Rare earth is easy to combine with oxygen, sulfur, lead and other elements to form compounds with high melting point. Therefore, adding rare earth into molten steel can play a role in purifying steel. Because the radius of metal atom of rare earth element is larger than that of iron atom, it is easy to fill in the grains and defects, and form a film which can hinder the continuous growth of grains, so as to refine the grains and improve the properties of steel.
Rare earth elements have an unfilled 4f electron layer structure, which leads to a variety of electronic energy levels. The orbital electrons in the 4f sublayer of lanthanide can not participate in the bonding because they are effectively shielded by the outer 5S and 5p layer electrons. Therefore, they have two very prominent characteristics: very similar chemical properties and obvious differences in physical properties, which create many opportunities for application and development. Therefore, rare earth can be used as excellent fluorescent, laser and electric light source materials and materials Glaze, colored glass.
Rare earth ions combine with hydroxyl, azo or sulfonic groups to form complexes, which make rare earth widely used in printing and dyeing industry. Some rare earth elements, such as samarium, europium, gadolinium, dysprosium and erbium, can be used as control materials and decelerants for nuclear reactors. Cerium and yttrium can be used as diluents for reactor fuel because of their small neutron capture cross section.
Rare earth is similar to trace elements, which can promote seed germination, root growth and Photosynthesis of crops.
Some physical properties of rare earth metals

原子序数	元素	原子量	离子半 径(埃)	密度 (克/厘3)	熔度 (℃)	沸点 (℃）	氧化物 熔点(℃)	氧化物 沸点(℃)	氯化物 熔点(℃)	氯化物 沸点(℃)
57	La镧	138.92	1.22	6.162	920	3464	2315	4200	858	1000
58	Ce铈	140.13	1.18	6.768	795	3443	2400	3500	817	1727
59	Pr镨	140.92	1.16	6.769	935	3130	2200		786	1710
60	Nd钕	144.27	1.15	7.007	1024	3074	2272		758	1600
61	Pm钷	147.00	1.14	－	－	－	－
62	Sm钐	150.35	1.13	7.52	1072	1900	2325		682
63	Eu铕	152.00	1.13	5.264	822	1529	2050		632
64	Gd钆	157.26	1.11	7.868	1312	3000	2340		609	1580
65	Tb铽	158.93	1.09	8.23	1356	3123	2200		558
66	Dy镝	162.51	1.07	8.540	1407	2562	2340		647	1530
67	Ho钬	164.94	1.05	8.799	1461	2600	2360		720	1500
68	Er铒	167.27	1.04	9.066	1529	2868	2355
69	Tm铥	168.94	1.04	9.318	1545	1950	2400
70	Yb镱	173.04	1.00	6.90	824	1196	2346
71	Lu镥	174.99	0.99	9.841	1652	3402	2490
21	Sc钪	44.97	0.83	2.985	1541	2836	2300
39	Y钇	88.92	1.06	4.472	1526	2930	2415

 

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原子序数	元素	电子排布		氧化态	氧化物颜色	热导率[瓦/(米.开)](25°C)	比电阻欧姆· 厘米×106	R3+离子磁矩 (波尔磁子)	总磁矩（波尔磁子）	热中子俘获 截面(靶恩)10=28米2
		电子排布	M3+
57	La镧	5d16S2	[Xe]	+3	白色	13.8	56.8	0.00	0.49	8.9
58	Ce铈	4f15d16S2	4f1	+3,+4	米色	10.9	75.3	2.56	2.51	0.7
59	Pr镨	4f36S2	4f2	+3,+4	黑色	11.7	68.0	3.62	3.56	11.2
60	Nd钕	4f46S2	4f3	+3	淡蓝	13.0	64.3	3.68	3.3	46
61	Pm钷	4f56S2	4f4	+3			－	2.83		－
62	Sm钐	4f66S2	4f5	+2,+3	淡黄		88.0	1.55～1.65	1.74	5500
63	Eu铕	4f76S2	4f6	+2,+3	微红白色		81.3	3.40～3.50	7.12	4600
64	Gd钆	4f75d16S2	4f7	+3	白色	8.8	140.5	7.94	7.95	46000
65	Tb铽	4f96S2	4f8	+3,+4	褐色	13.0	136	9.7	9.7	44
66	Dy镝	4f106S2	4f9	+3	白色	10.0	56.0	10.6	10.64	1150
67	Ho钬	4f116S2	4f10	+3	淡黄色		87.0	10.6	10.89	64
68	Er铒	4f126S2	4f11	+3	粉色	9.6	107.0	9.6	9.5	166
69	Tm铥	4f135S2	4f12	+3	淡绿		79.0	7.6	7.62	118
70	Yb镱	4f146S2	4f13	+2,+3	白色		27.0	4.5	0.41	36
71	Lu镥	4f145d16S2	4f14	+3	白色