Rare Earth Metals
A rare earth metal is one of seventeen elements that are shown in the table below. Rare Earths are often found in large deposits that have many different elements in the same deposit. Rare earths are divided into two categories, light rare earth elements “LREE” and heavy rare earth elements “HREE” which are usually found together.
Composition of Rare Earth
According to the International Union of Pure and Applied Chemistry (IUPAC), rare earth elements are represented by a group of 17 elements from the periodic table, inc luding scandium (Sc), yttrium (Y), and the 15 elements having atomic numbers between 57 and 71 (also known as lanthanoids or lanthanides) positioned just below scandium and yttrium, as shown in table below.
The lanthanoids have a xenon (Xe) core electron configuration with the addition of electrons in the 4f, 5d, and 6s orbital’s. Most lanthanoids tend to lose three electrons from these orbital’s (i.e., they have a valence of 3), with the exception of cerium, which can also have a valence of 4, and samarium, europium, and ytterbium, which can also be bivalent.
Lanthanoids are divided into two groups: light rare earths (LREE), which include the elements from lanthanum to samarium, and heavy rare earths (HREE), which include the elements from europium to lutetium. Sometimes, samarium, europium, and gadolinium are referred to as medium rare earths (MREE).
Rare Earths in the periodic table
|
1
H
1.0
|
2
He
4.0
|
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|
3
Li
6.9
|
4
Be
9.0
|
5
B
10.8
|
6
C
12.0
|
7
N
16.0
|
8
O
15.9
|
9
F
18.99
|
Ne
20.18
|
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|
11
Na
23
|
12
Mg
24.3
|
13
Al
27
|
14
Si
28
|
15
P
|
16
S
31
|
17
Cl
32
|
18
Ar
40
|
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|
19
K
39
|
20
Ca
40
|
21
Sc
44
|
22
Ti
48
|
23
V
50.9
|
24
Cr
52
|
25
Mn
54.9
|
26
Fe
55.9
|
27
Co
58.9
|
28
Ni
58.6
|
29
Cu
63.5
|
30
Zn
65.3
|
31
Ga
69.7
|
32
Ge
72.6
|
33
As
74.9
|
34
Se
78
|
35
Br
80
|
36
Kr
84.8
|
|
37
Rb
84.4
|
38
Sr
87.6
|
39
Y
88.9
|
40
Zr
91.2
|
41
Nb
92.9
|
42
Mo
95.9
|
43
Tc
98.9
|
44
Ru
101
|
45
Rh
103
|
46
Pd
106.4
|
47
Ag
107.8
|
48
Cd
112.4
|
49
In
114.8
|
50
Sn
118.7
|
51
Sb
121.7
|
52
Te
127.6
|
53
I
126.9
|
54
Xe
131.2
|
|
55
Cs
132.9
|
56
Ba
137.3
|
57-71
|
72
Hf
178.4
|
73
Ta
180.9
|
74
W
183.8
|
75
Re
186.2
|
76
Os
190.2
|
77
Ir
192.2
|
78
Pt
195
|
79
Au
196.9
|
80
Hg
200.5
|
81
Tl
204.3
|
82
Pb
207.2
|
83
Bi
208.9
|
84
Po
208.98
|
85
At
209.9
|
86
Rn
222
|
|
87
Fr
223
|
88
Ra
226
|
89-103
|
104
Rf
261
|
105
Db
262
|
106
Sg
266
|
107
Bh
264
|
108
Hs
269
|
109
Mt
268
|
110
Ds
269
|
111
Rg
272
|
112
Cn
277
|
113
Uut
|
114
Fl
289
|
115
Uup
|
116
Lv
298
|
117
Uus
|
118
Uuo
|
|
*
Lanthanides
|
57
La
136.9
|
58
Ce
140.1
|
59
Pr
140.9
|
60
Nd
144.2
|
61
Pm
144.9
|
62
Sm
150.3
|
63
Eu
151.9
|
64
Gd
157.25
|
65
Tb
158.9
|
66
Dy
162.5
|
67
Ho
164.9
|
68
Er
167.2
|
69
Tm
168.9
|
70
Yb
173
|
71
Lu
174.9
|
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|
**
Actinides
|
89
Ac
227
|
90
Th
232.03
|
91
Pa
231.3
|
92
U
238
|
93
Np
237
|
94
Pu
244
|
95
Am
243
|
96
Cm
247
|
97
Bk
247
|
98
Cf
251
|
99
Es
254
|
100
Fm
257
|
101
Md
258
|
102
No
259
|
103
Lr
262
|
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