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 |
密度 |
熔度 |
沸点 |
氧化物 |
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 |
|
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 |
总磁矩（波尔磁子） |
热中子俘获 |
|
| 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 | |||||
