Ionic radius (Å) – Seto's Page

This data is taken from Shannon, R. D., Acta Crystallogr. A32, 751, 1976. Please refer to the original article for the meaning of the detailed notation. Note that Shannon’s ionic radii are not given for all valence and coordination numbers. Recently, the ionic radii have been estimated by machine learning (click here).

SQ: Square planar coordination
PY: Pyramidal coordination

R: From r³ vs. V plots
C: Calculated from bond length-bond strength equations.
E: Estimated from one or more plots of r vs. valence, r vs. CN, and r vs. cell volume.

?: Doubtful
*: Most reliable
A: Ahrens (1952) ionic radius
P: Pauling’s (1960) crystal radius
M: From a compound having metallic conductivity.

Element	Valence	Coordination	Crystal radius	Ionic radius	Orbit	Note
1H	+1		-0.24	-0.38	1s0
1H	+1	2	-0.04	-0.18	1s0
2He	–	–	–	–
3Li	+1	4	0.73	0.59	1s2	*
		6	0.90	0.76		*
		8	1.06	0.92		C
4Be	+2	3	0.30	0.16	1s2
		4	0.41	0.27		*
		6	0.59	0.45		C
5B	+3	3	0.15	0.01	1s2	*
		4	0.25	0.11		*
		6	0.41	0.27		C
6C	+4	3	0.06	-0.08	1s2	C
		4	0.29	0.15		P
		6	0.30	0.16		A
7N	-3	4	1.32	1.46	2p6
	+3	6	0.30	0.16	2s2	A
	+5	3	0.044	-0.104	1s2
	+5	6	0.27	0.13	1s2	A
8 O	-2	2	1.21	1.35	2p6
		3	1.22	1.36
		4	1.24	1.38
		6	1.26	1.40
		8	1.28	1.42
9F	-1	2	1.145	1.285	2p6
		3	1.16	1.30
		4	1.17	1.31
		6	1.19	1.33
	7	6	0.22	0.08	1s2	A
10Ne	–	–	–	–	2p6
11Na	+1	4	1.13	0.99	2p6
		5	1.14	1.00
		6	1.16	1.02
		7	1.26	1.12
		8	1.32	1.18
		9	1.38	1.24		C
		12	1.53	1.39
12Mg	+2	4	0.71	0.57	2p6
		5	0.80	0.66
		6	0.86	0.72		*
		8	1.03	0.89		C
13Al	+3	4	0.53	0.39	2p6	*
		5	0.62	0.48
		6	0.675	0.535		R*
14Si	+4	4	0.40	0.26	2p6	*
14Si	+4	6	0.54	0.40	2p6	R*
15P	+3	6	0.58	0.44	3s2	A
	+5	4	0.31	0.17	2p6	*
		5	0.43	0.29
		6	0.52	0.38		C
16S	-2	6	1.70	1.84	3p6	P
	+4	6	0.51	0.37	3s2	A
	+6	4	0.26	0.12	2p6	*
	+6	6	0.43	0.29	2p6	C
17Cl	-1	6	1.67	1.81	3p6	P
	+5	3PY	0.26	0.12	3s2
	+7	4	0.22	0.08	2p6	*
	+7	6	0.41	0.27	2p6	A
18Ar	–	–	–	–	3p6
19K	+1	4	1.51	1.37	3p6
		6	1.52	1.38
		7	1.60	1.46
		8	1.65	1.51
		9	1.69	1.55
		10	1.73	1.59
		12	1.78	1.64
20Ca	+2	6	1.14	1.00	3p6
		7	1.20	1.06		*
		8	1.26	1.12		*
		9	1.32	1.18
		10	1.37	1.23		C
		12	1.48	1.34		C
21Sc	+3	6	0.885	0.745	3p6	R*
21Sc	+3	8	1.01	0.87	3p6	R*
22Ti	+2	6	1.00	0.86	3d2	E
	+3	6	0.81	0.67	3d1	R*
	+4	4	0.56	0.42	3p6	C
		5	0.65	0.51		C
		6	0.745	0.605		R*
		8	0.88	0.74		C
23V	+2	6	0.93	0.79	3d3
	+3	6	0.78	0.64	3d2	R*
	+4	5	0.67	0.53	3d1
		6	0.72	0.58		R*
		8	0.86	0.72		E
	+5	4	0.495	0.355	3p6	R*
		5	0.60	0.46		*
		6	0.68	0.54
24Cr	+2	6	0.87	0.73	3d4	E
	+2	6	0.94	0.80	3d4	R
	+3	6	0.755	0.615	3d3	R*
	+4	4	0.55	0.41	3d2
	+4	6	0.69	0.55	3d2	R
	+5	4	0.485	0.345	3d1	R
		6	0.63	0.49		ER
		8	0.71	0.57
	+6	4	0.40	0.26	3p6
	+6	6	0.58	0.44	3p6	C
25Mn	+2	4	0.80	0.66	3d5
		5	0.89	0.75		C
		6	0.81	0.67		E
		6	0.97	0.83		R*
		7	1.04	0.90		C
		8	1.10	0.96		R
	+3	5	0.72	0.58	3d4
		6	0.72	0.58		R
		6	0.785	0.645		R*
	+4	4	0.53	0.39	3d3	R
	+4	6	0.67	0.53	3d3	R*
	+5	4	0.47	0.33	3d2	R
	+6	4	0.395	0.255	3d1
	+7	4	0.39	0.25	3p6
	+7	6	0.60	0.46	3p6	A
26Fe	+2	4	0.77	0.63	3d6
		4SQ	0.78	0.64
		6	0.75	0.61		E
		6	0.92	0.78		R*
		8	1.06	0.92		C
	+3	4	0.63	0.49	3d5	*
		5	0.72	0.58
		6	0.69	0.55		R
		6	0.785	0.645		R*
		8	0.92	0.78
	+4	6	0.725	0.585	3d4	R
	+6	4	0.39	0.25	3d2	R
27Co	+2	4	0.72	0.58	3d7
		5	0.81	0.67		C
		6	0.79	0.65		R
		6	0.885	0.745		R*
		8	1.04	0.90
	+3	6	0.685	0.545	3d6	R*
	+3	6	0.75	0.61	3d6
	+4	4	0.54	0.4	3d5
	+4	6	0.67	0.53	3d5	R
28Ni	+2	4	0.69	0.55	3d8
		4SQ	0.63	0.49
		5	0.77	0.63		E
		6	0.83	0.69		R*
	+3	6	0.70	0.56	3d7	R*
	+3	6	0.74	0.60	3d7	E
	+4	6	0.62	0.48	3d6	R
29Cu	+1	2	0.60	0.46	3d10
		4	0.74	0.6		E
		6	0.91	0.77		E
	+2	4	0.71	0.57	3d9
		4SQ	0.71	0.57		*
		5	0.79	0.65		*
		6	0.87	0.73
	+3	6	0.68	0.54	3d8
30Zn	+2	4	0.74	0.60	3d10	*
		5	0.82	0.68		*
		6	0.88	0.74		*
		8	1.04	0.90		R*
31Ga	+3	4	0.61	0.47	3d10	*
		5	0.69	0.55
		6	0.76	0.62		R*
32Ge	+2	6	0.87	0.73	4s2	A
	+4	4	0.53	0.39	3d10	*
	+4	6	0.67	0.53	3d10	R*
33As	+3	6	0.72	0.58	4s2	A
	+5	4	0.475	0.335	3d10	R*
	+5	6	0.60	0.46	3d10	C*
34Se	-2	6	1.84	1.98	4p6	P
	+4	6	0.64	0.50	4s2	A
	+6	4	0.42	0.28	3d10	*
	+6	6	0.56	0.42	3d10	C
35Br	-1	6	1.82	1.96	4p6	P
	+3	4SQ	0.73	0.59	4p2
	+5	3PY	0.45	0.31	4s2
	+7	4	0.39	0.25	3d10
	+7	6	0.53	0.39	3d10	A
36Kr	–	–	–	–	4p6
37Rb	+1	6	1.66	1.52	4p6
		7	1.70	1.56
		8	1.75	1.61
		9	1.77	1.63		E
		10	1.80	1.66
		11	1.83	1.69
		12	1.86	1.72
			1.97	1.83
38Sr	+2	6	1.32	1.18	4p6
		7	1.35	1.21
		8	1.40	1.26
		9	1.45	1.31
		10	1.50	1.36		C
		12	1.58	1.44		C
39Y	+3	6	1.04	0.90	4p6	R*
		7	1.10	0.96
		8	1.159	1.019		R*
		9	1.215	1.075		R
40Zr	+4	4	0.73	0.59	4p6	R
		5	0.80	0.66		C
		6	0.86	0.72		R*
		7	0.92	0.78		*
		8	0.98	0.84		*
		9	1.03	0.89
41Nb	+3	6	0.86	0.72	4d2
	+4	6	0.82	0.68	4d1	RE
	+4	8	0.93	0.79	4d1
	+5	4	0.62	0.48	4p6	C
		6	0.78	0.64
		7	0.83	0.69		C
		8	0.88	0.74
42Mo	+3	6	0.83	0.69	4d3	E
	+4	6	0.79	0.65	4d2	RM
	+5	4	0.60	0.46	4d1	R
	+5	6	0.75	0.61	4d1	R
	+6	4	0.55	0.41	4p6	R*
		5	0.73	0.59
		6	0.73	0.59		R*
		7	0.87	0.73
43Tc	+4	6	0.785	0.645	4d3	RM
	+5	6	0.74	0.60	4d2	ER
	+7	4	0.51	0.37	4p6
	+7	6	0.7	0.56	4p6	A
44Ru	+3	6	0.82	0.68	4d5
	+4	6	0.76	0.62	4d4	RM
	+5	6	0.705	0.565	4d3	ER
	+7	4	0.52	0.38	4d1
	+8	4	0.50	0.36	4p6
45Rh	+3	6	0.805	0.665	4d6	R
	+4	6	0.74	0.6	4d5	RM
	+5	6	0.69	0.55	4d4
46Pd	+1	2	0.73	0.59	4d9
	+2	4SQ	0.78	0.64	4d8
	+2	6	1.00	0.86	4d8
	+3	6	0.90	0.76	4d7
	+4	6	0.755	0.615	4d6	R
47Ag	+1	2	0.81	0.67	4d10
		4	1.14	1.00		C
		4SQ	1.16	1.02
		5	1.23	1.09		C
		6	1.29	1.15		C
		7	1.36	1.22
		8	1.42	1.28
	+2	4SQ	0.93	0.79	4d9
	+2	6	1.08	0.94	4d9
	+3	4SQ	0.81	0.67	4d8
	+3	6	0.89	0.75	4d8	R
48Cd	+2	4	0.92	0.78	4d10
		5	1.01	0.87
		6	1.09	0.95
		7	1.17	1.03		C
		8	1.24	1.1		C
		12	1.45	1.31
49In	+3	4	0.76	0.62	4d10
		6	0.94	0.80		R*
		8	1.06	0.92		RC
50Sn	+4	4	0.69	0.55	4d10	R
		5	0.76	0.62		C
		6	0.83	0.69		R*
		7	0.89	0.75
		8	0.95	0.81		C
51Sb	+3	4PY	0.9	0.76	5s2
		5	0.94	0.8
		6	0.90	0.76		A
	+5	6	0.74	0.60	4d10	*
52Te	-2	6	2.07	2.21	5p6	P
	+4	3	0.66	0.52	5s2
		4	0.80	0.66
		6	1.11	0.97
	+6	4	0.57	0.43	4d10	C
	+6	6	0.7	0.56	4d10	*
53I	-1	6	2.06	2.2	5p6	A
	+5	3PY	0.58	0.44	5s2	*
	+5	6	1.09	0.95	5s2
	+7	4	0.56	0.42	4d10
	+7	6	0.67	0.53	4d10
54Xe	+8	4	0.54	0.40	4d10
54Xe	+8	6	0.62	0.48	4d10
55Cs	+1	6	1.81	1.67	5p6
		8	1.88	1.74
		9	1.92	1.78
		10	1.95	1.81
		11	1.99	1.85
		12	2.02	1.88
56Ba	+2	6	1.49	1.35	5p6
		7	1.52	1.38		C
		8	1.56	1.42
		9	1.61	1.47
		10	1.66	1.52
		11	1.71	1.57
		12	1.75	1.61		C
57La	+3	6	1.172	1.032	4d10	R
		7	1.24	1.10
		8	1.30	1.16		R
		9	1.356	1.216		R
		10	1.41	1.27
		12	1.50	1.36		C
58Ce	+3	6	1.15	1.01	6s1	R
		7	1.21	1.07		E
		8	1.283	1.143		R
		9	1.336	1.196		R
		10	1.39	1.25
		12	1.48	1.34		C
	+4	6	1.01	0.87	5p6	R
		8	1.11	0.97		R
		10	1.21	1.07
		12	1.28	1.14
59Pr	+3	6	1.13	0.99	4f2	R
		8	1.266	1.126		R
		9	1.319	1.179		R
	+4	6	0.99	0.85	4f1	R
	+4	8	1.10	0.96	4f1	R
60Nd	+2	8	1.43	1.29	4f4
	+2	9	1.49	1.35	4f4
	+3	6	1.123	0.983	4f3	R
		8	1.249	1.109		R*
		9	1.303	1.163		R
		12	1.41	1.27		E
61Pm	+3	6	1.11	0.97	4f4	R
		8	1.233	1.093		R
		9	1.284	1.144		R
52Sm	+2	7	1.36	1.22	4f6
		8	1.41	1.27
		9	1.46	1.32
	+3	6	1.098	0.958	4f5	R
		7	1.16	1.02		E
		8	1.219	1.079		R
		9	1.272	1.132		R
		12	1.38	1.24		C
63Eu	+2	6	1.31	1.17	4f7
		7	1.34	1.20
		8	1.39	1.25
		9	1.44	1.3
		10	1.49	1.35
	+3	6	1.087	0.947	4f6	R
		7	1.15	1.01
		8	1.206	1.066		R
		9	1.26	1.12		R
64Gd	+3	6	1.078	0.938	4f7	R
		6	1.14	1.00
		8	1.193	1.053		R
		9	1.247	1.107		RC
65Tb	+3	6	1.063	0.923	4f8	R
		7	1.12	0.98		E
		8	1.18	1.04		R
		9	1.235	1.095		R
	+4	6	0.90	0.76	4f7	R
	+4	8	1.02	0.88	4f7
66Dy	+2	6	1.21	1.07	4f10
		7	1.27	1.13
		8	1.33	1.19
	+3	6	1.052	0.912	4f9	R
		7	1.11	0.97
		8	1.167	1.027		R
		9	1.223	1.083		R
67Ho	+3	6	1.041	0.901	4f10	R
		8	1.155	1.015		R
		9	1.212	1.072		R
		10	1.26	1.12
68Er	+3	6	1.03	0.89	4f11	R
		7	1.085	0.945
		8	1.144	1.004		R
		9	1.202	1.062		R
69Tm	+2	6	1.17	1.03	4f13
	+2	7	1.23	1.09	4f13
	+3	6	1.02	0.88	4f12	R
		8	1.134	0.994		R
		9	1.192	1.052		R
70Yb	+2	6	1.16	1.02	4f14
		7	1.22	1.08		E
		8	1.28	1.14
	+3	6	1.008	0.868	4f13	R*
		7	1.065	0.925		E
		8	1.125	0.985		R
		9	1.182	1.042		R
71Lu	+3	6	1.001	0.861	4f14	R
		8	1.117	0.977		R
		9	1.172	1.032		R
72Hf	+4	4	0.72	0.58	4f14	R
		6	0.85	0.71		R
		7	0.90	0.76
		8	0.97	0.83
73Ta	+3	6	0.86	0.72	5d2	E
	+4	6	0.82	0.68	5d1	E
	+5	6	0.78	0.64	5p6
		7	0.83	0.69
		8	0.88	0.74
74W	+4	6	0.80	0.66	5d2	RM
	+5	6	0.76	0.62	5d1	R
	+6	4	0.56	0.42	5d6	*
		5	0.65	0.51
		6	0.74	0.6		*
75Re	+4	6	0.77	0.63	5d3	RM
	+5	6	0.72	0.58	5d2	E
	+6	6	0.69	0.55	5d1	E
	+7	4	0.52	0.38	5p6
	+7	6	0.67	0.53	5p6
76Os	+4	6	0.77	0.63	5d4	RM
	+5	6	0.715	0.575	5d3	E
	+6	5	0.63	0.49	5d2
	+6	6	0.685	0.545	5d2	E
	+7	6	0.665	0.525	5d1	E
	+8	4	0.53	0.39	5p6
77Ir	+3	6	0.82	0.68	5d6	E
	+4	6	0.765	0.625	5d5	R
	+5	6	0.71	0.57	5d4	EM
78Pt	+2	4SQ	0.74	0.60	5d8
	+2	6	0.94	0.80	5d8	A
	+4	6	0.765	0.625	5d6	R
	+5	6	0.71	0.57	5d5	ER
79Au	+1	6	1.51	1.37	5d10	A
	+3	4SQ	0.82	0.68	5d8
	+3	6	0.99	0.85	5d8	A
	+5	6	0.71	0.57	5d6
80Hg	+1	3	1.11	0.97	6s1
	+1	6	1.33	1.19	6s1
	+2	2	0.83	0.69	5d10
		6	1.10	0.96
		8	1.28	1.14		R
81Tl	+1	6	1.64	1.5	6s2	R
		8	1.73	1.59		R
		12	1.84	1.70		RE
	+3	4	0.89	0.75	5d10
		6	1.025	0.885		R
		8	1.12	0.98		C
82Pb	+2	4PY	1.12	0.98	6s2	C
		6	1.33	1.19
		7	1.37	1.23		C
		8	1.43	1.29		C
		9	1.49	1.35		C
		10	1.54	1.40		C
		11	1.59	1.45		C
		12	1.63	1.49
	+4	4	0.79	0.65	5d10	E
		5	0.87	0.73		E
		6	0.915	0.775		R
		8	1.08	0.94		R
83Bi	+3	5	1.1	0.96	6s2	C
		6	1.17	1.03		R*
		8	1.31	1.17		R
	+5	6	0.90	0.76	5d10	E
84Po	+4	6	1.08	0.94	6s2	R
	+4	8	1.22	1.08	6s2	R
	+6	6	0.81	0.67	5d10	A
85At	+7	6	0.76	0.62	5d10	A
86Rn	–	–	–	–	6p6
87Fr	+1	6	1.94	1.80	6p6	A
88Ra	+2	8	1.62	1.48	6p6	R
88Ra	+2	12	1.84	1.70	6p6	R
89Ac	+3	6	1.26	1.12	6p6	R
90Th	+4	6	1.08	0.94	6p6	C
		8	1.19	1.05		RC
		9	1.23	1.09		*
		10	1.27	1.13		E
		11	1.32	1.18		C
		12	1.35	1.21		C
91Pa	+3	6	1.18	1.04	5f2	E
	+4	6	1.04	0.9	6d1	R
	+4	8	1.15	1.01	6d1
	+5	6	0.92	0.78	6p6
		8	1.05	0.91
		9	1.09	0.95
92U	+3	6	1.165	1.025	5f3	R
	+4	6	1.03	0.89	5f2
		7	1.09	0.95		E
		8	1.14	1.00		R*
		9	1.19	1.05
		12	1.31	1.17		E
	+5	6	0.90	0.76	5f1
	+5	7	0.98	0.84	5f1	E
	+6	2	0.59	0.45	6p6
		4	0.66	0.52
		6	0.87	0.73		*
		7	0.95	0.81		E
		8	1.00	0.86
93Np	+2	6	1.24	1.10	5f5
	+3	6	1.15	1.01	5f4	R
	+4	6	1.01	0.87	5f3	R
	+4	8	1.12	0.98	5f3	R
	+5	6	0.89	0.75	5f2
	+6	6	0.86	0.72	5f1	R
	+7	6	0.85	0.71	6p6	A
94Pu	+3	6	1.14	1.00	5f5	R
	+4	6	1.00	0.86	5f4	R
	+4	8	1.10	0.96	5f4
	+5	6	0.88	0.74	5f3	E
	+6	6	0.85	0.71	5f2	R
95Am	+2	7	1.35	1.21	5f7
		8	1.40	1.26
		9	1.45	1.31
	+3	6	1.115	0.975	5f6	R
	+3	8	1.23	1.09	5f6
	+4	6	0.99	0.85	5f5	R
	+4	8	1.09	0.95	5f5
96Cm	+3	6	1.11	0.97	5f7	R
	+4	6	0.99	0.85	5f6	R
	+4	8	1.09	0.95	5f6	R
97Bk	+3	6	1.10	0.96	5f8	R
	+4	6	0.97	0.83	5f7	R
	+4	8	1.07	0.93	5f7	R
98Cf	+3	6	1.09	0.95	6d1	R
	+4	6	0.961	0.821	5f8	R
	+4	8	1.06	0.92	5f8
Element	Valence	Coordinate	Crystal radius	Ionic radius	Orbit	Note