0.52, 0.66
|
1.13, 0.98
|
2.1
|
|
Ti4+
|
4, 6
|
0.42, 0.61
|
1.26, 1.03
|
1.5
|
|
Ge4+
|
4, 6
|
0.39, 0.53
|
1.31, 1.12
|
1.8
|
|
Si4+
|
4, 6
|
0.26, 0.40
|
1.52, 1.29
|
1.8
|
|
B3+
|
3, 4
|
0.01, 0.11
|
1.60, 1.41
|
2.0
|
|
P5+
|
4
|
0.17
|
2.14
|
2.1
|
|
Modifier to intermediate: alkalis and alkaline earths
|
|
Cs1+
|
8
|
1.74
|
0.10
|
0.7
|
|
Rb1+
|
8
|
1.61
|
0.11
|
0.8
|
|
K1+
|
8
|
1.51
|
0.12
|
0.8
|
|
Na1+
|
6
|
1.02
|
0.18
|
0.9
|
|
Li1+
|
4, 6
|
0.59, 0.76
|
0.26, 0.22
|
1.0
|
|
Ba2+
|
8
|
1.42
|
0.26
|
0.9
|
|
Sr2+
|
8
|
1.26
|
0.29
|
1.0
|
|
Ca2+
|
6, 8
|
1.00, 1.12
|
0.36, 0.33
|
1.0
|
|
Mg2+
|
4, 6
|
0.57, 0.72
|
0.53, 0.46
|
1.2
|
|
Be2+
|
4
|
0.27
|
0.75
|
1.5
|
|
Modifier to intermediate: selected others
|
|
Sn2+
|
8e
|
1.26
|
0.29
|
1.8
|
|
Pb2+
|
4, 8e
|
0.98, 1.29
|
0.37, 0.28
|
1.9
|
|
Mn2+
|
6
|
0.83f
|
0.42
|
1.5
|
|
Fe2+
|
6
|
0.78f
|
0.44
|
1.8
|
|
Zn2+
|
4, 6
|
0.60, 0.74
|
0.52, 0.45
|
1.6
|
|
Ni2+
|
4, 6
|
0.55, 0.69
|
0.55, 0.48
|
1.9
|
|
La3+
|
8
|
1.16
|
0.47
|
1.1
|
|
Nd3+
|
8
|
1.11
|
0.49
|
1.1
|
|
Er3+
|
8
|
1.00
|
0.54
|
1.2
|
|
Y3+
|
8
|
1.02
|
0.53
|
1.2
|
|
Sc3+
|
6
|
0.75
|
0.67
|
1.3
|
|
Sb3+
|
4e
|
0.76
|
0.67
|
1.9
|
|
Zr4+
|
8
|
0.84
|
0.83
|
1.4
|
|
U4+
|
6
|
0.89
|
0.79
|
1.7
|
|
Mo6+
|
4, 6
|
0.41, 0.59
|
1.92, 1.58
|
1.8
|
a Common coordination numbers; others may occur. Five‐coordinate states are also known for many cations listed with 4 and 6 coordination (e.g. Al, Si, Ti, Ni), which have intermediate radii and field strengths.
b Cation field strength, valence divided by square of cation–oxygen distance, with the radius of the latter taken as 1.36 Å, the typical value for three‐coordinated O.
c Pauling electronegativity, from Pauling, L. (1970). General Chemistry. San Francisco: W.H. Freeman.
d “Network former” description is generally most appropriate for lower coordination numbers.
e Lone‐pair electronic structure may lead to lower coordination than expected from radius.
f
