6: Trends in ionic radii of lanthanoids
Rationalised 2023-24
110
Chemistry
Electronic configurations*
Radii/pm
Atomic
 Name
Symbol
 Ln
Ln
2+
Ln
3+
Ln
4+
Ln
Ln
3+
Number
57
Lanthanum
La
5d
16s
2
5d
1
4f 
0
187
106
58
Cerium
Ce
4f
15d
16s
2
4f 
2
4f 
1
4f 
0
183
103
59
Praseodymium
Pr
4f 
36s
2
4f 
3
4f 
2
4f 
1
182
101
60
Neodymium
Nd
4f 
46s
2
4f 
4
4f 
3
4f 
2
181
99
61
Promethium
Pm
4f 
56s
2
4f 
5
4f 
4
181
98
62
Samarium
Sm
4f 
66s
2
4f 
6
4f 
5
180
96
63
Europium
Eu
4f 
76s
2
4f 
7
4f 
6
199
95
64
Gadolinium
Gd
4f 
75d
16s
2
4f 
75d
1
4f 
7
180
94
65
Terbium
Tb
4f 
96s
2
4f 
9
4f 
8
4f 
7
178
92
66
Dysprosium
Dy
4f 
106s
2
4f 
10
4f 
9
4f 
8
177
91
67
Holmium
Ho
4f 
116s
2
4f 
11
4f 
10
176
89
68
Erbium
Er
4f 
126s
2
4f 
12
4f 
11
175
88
69
Thulium
Tm
4f 
136s
2
4f 
13
4f 
12
174
87
70
Ytterbium
Yb
4f 
146s
2
4f 
14
4f 
13
173
86
71
Lutetium
Lu
4f 
145d
16s
2
4f 
145d
1
4f 
14
–
–
–
Table 4 9: Electronic Configurations and Radii of Lanthanum and Lanthanoids
* Only electrons outside [Xe] core are indicated
All the lanthanoids are silvery white soft metals and tarnish rapidly in air The hardness increases with increasing atomic number, samarium being
steel hard Their melting points range between 1000 to 1200 K but
samarium melts at 1623 K