Table 1. Bond-length statistics for the five common alkali-metal ions.

Ion	Coordination number	Number of bonds	Number of coordination polyhedra	Mean bond length (Å)	Standard deviation (Å)	Range (Å)	Maximum bond length (Å)	Minimum bond length (Å)	Skewness	Kurtosis
Li+	3	12	4	1.913	0.040	0.113	1.984	1.871	–	–
	4	1676	419	1.972	0.075	0.754	2.444	1.690	1.563	6.273
	5	455	91	2.108	0.161	0.858	2.673	1.815	1.265	1.362
	6	1038	173	2.178	0.137	0.866	2.692	1.826	1.293	1.996
	7	14	2	2.331	0.244	0.728	2.658	1.930	–	–
	8	8	1	2.513	0.000	0.000	2.513	2.513	–	–
	Total	3203	690
Na+	3	21	7	2.307	0.045	0.153	2.367	2.214	–	–
	4	524	131	2.359	0.076	0.586	2.775	2.189	0.878	2.032
	5	710	142	2.413	0.108	0.808	2.968	2.160	1.455	3.522
	6	5520	920	2.441	0.112	0.926	3.055	2.129	1.317	3.246
	7	1351	193	2.541	0.180	1.002	3.180	2.178	0.723	−0.020
	8	1608	201	2.599	0.192	1.069	3.211	2.142	0.461	−0.197
	9	450	50	2.686	0.224	1.044	3.204	2.160	0.121	−0.879
	10	170	17	2.741	0.240	0.899	3.156	2.257	−0.063	−1.075
	12	252	21	2.795	0.182	0.950	3.272	2.322	0.053	−0.295
	Total	10606	1682
K+	4	96	24	2.708	0.078	0.365	2.892	2.527	–	–
	5	295	59	2.796	0.162	1.032	3.537	2.505	1.404	3.349
	6	714	119	2.828	0.177	1.140	3.587	2.447	1.299	2.268
	7	469	67	2.861	0.179	1.030	3.554	2.524	1.269	1.474
	8	2272	284	2.894	0.172	1.107	3.644	2.537	1.195	1.642
	9	2772	308	2.955	0.214	1.306	3.797	2.491	1.079	0.917
	10	2430	243	3.013	0.246	1.248	3.773	2.525	0.839	0.084
	11	957	87	3.089	0.290	1.181	3.793	2.612	0.550	−0.763
	12	2328	194	3.095	0.264	1.204	3.790	2.586	0.578	−0.535
	13	455	35	3.149	0.298	1.290	3.808	2.518	0.364	−0.834
	14	336	24	3.239	0.296	1.292	3.771	2.479	0.057	−0.929
	15	525	35	3.182	0.265	1.148	3.748	2.600	0.257	−1.164
	Total	13649	1479
Rb+	4	48	12	2.951	0.160	0.706	3.360	2.654	–	–
	5	15	3	2.864	0.078	0.236	2.976	2.740	–	–
	6	84	14	2.989	0.148	0.734	3.488	2.754	–	–
	7	140	20	3.002	0.186	0.937	3.628	2.691	1.283	1.554
	8	480	60	3.033	0.190	1.055	3.711	2.656	1.030	1.236
	9	675	75	3.079	0.204	1.172	3.839	2.667	0.980	1.192
	10	1080	108	3.146	0.244	1.171	3.890	2.719	0.858	0.081
	11	484	44	3.188	0.248	1.211	3.884	2.673	0.725	−0.242
	12	840	70	3.228	0.288	1.181	3.896	2.715	0.545	−0.663
	13	247	19	3.293	0.314	1.148	3.932	2.784	0.376	−1.163
	14	280	20	3.301	0.291	1.151	3.895	2.744	0.332	−0.938
	15	195	13	3.338	0.278	1.065	3.945	2.880	0.485	−0.934
	17	17	1	3.456	0.336	1.009	3.939	2.930	–	–
	18	90	5	3.478	0.239	0.695	3.771	3.076	–	–
	Total	4675	464
Cs+	6	102	17	3.124	0.139	0.702	3.568	2.866	0.922	1.040
	7	70	10	3.193	0.166	0.858	3.806	2.948	–	–
	8	200	25	3.244	0.189	1.017	3.911	2.894	0.863	0.708
	9	432	48	3.251	0.181	1.052	3.882	2.830	0.656	0.186
	10	930	93	3.304	0.208	1.257	3.986	2.729	0.696	0.174
	11	748	68	3.333	0.226	1.136	4.023	2.887	0.630	−0.106
	12	1080	90	3.377	0.250	1.162	4.072	2.910	0.670	−0.437
	13	520	40	3.426	0.276	1.256	4.130	2.874	0.480	−0.571
	14	714	51	3.444	0.297	1.242	4.169	2.927	0.528	−0.764
	15	705	47	3.503	0.301	1.253	4.157	2.904	0.241	−0.953
	16	224	14	3.550	0.321	1.276	4.199	2.923	0.341	−0.870
	17	68	4	3.530	0.326	1.069	4.060	2.991	–	–
	18	648	36	3.570	0.277	1.243	4.195	2.952	−0.010	−0.807
	20	20	1	3.723	0.419	0.855	4.065	3.210	–	–
	Total	6461	544