. 2020 Jul 20;21(16):1742–1767. doi: 10.1002/cphc.202000162

Table 1.

Selected ion properties. Unless indicated otherwise, the ionic radii are taken from Table 2.2 in Ref. 88. ^a indicates an approximate value,88 ^b from Ref. 89; ^c from Ref. 90; ^d from Ref. 91 ^e from Ref. 92.

Ion	Radius in solution (nm)	Hydration number	Electron configuration
Na⁺	0.102	3.5	[Ne] 3s⁰
K⁺	0.138	2.6	[Ar] 4s⁰
Mg²⁺	0.072	10.0	[Ne] 3s⁰
Ca²⁺	0.100	7.2	[Ar] 4s⁰
Fe³⁺	0.065	6.0^e	[Ar] 3d⁵
Y³⁺	0.102^b	8.0^d	[Kr] 4p⁰ 5s⁰
La³⁺	0.125^c	10.3	[Xe] 4f⁰
(CH₃)₄N⁺	0.280	1.3	–
Cl⁻	0.181	2.0	[Ne] 3s² 3p⁶
F⁻	0.133	2.7	[He] 2s² 2p⁶
CO $_{3}^{2 -}$	0.178^a	4.0
SO $_{4}^{2 -}$	0.230	3.1
PO $_{4}^{3 -}$	0.238	4.5