X-ray diffraction studies on scandium salts in solution and in the solid state, have afforded Sc-O bond lengths in the ions [Sc(H2O)n]³⁺ (n = 6, 7 and 8) as well as for several compounds containing [(H₂O)₅Sc(μ-OH)₂Sc(H₂O)₅]⁴⁺ ions. Several theoretical studies have examined different models for the aqua ion without finding agreement. This review considers these studies. Diffraction results from solutions yield bond lengths which are compared with species of known geometry and coordination number in the solid state, and with different quantum mechanical predictions. On balance, it is considered that a seven-coordinate [Sc(OH2)7]³⁺ ion is the species found in solution.

对溶液和固态scan盐的X射线衍射研究提供了离子[Sc（H2O）n] ³⁺（n = 6、7和8）以及几种化合物的Sc-O键长含有[（H ₂ O）₅ Sc（μ-OH）₂ Sc（H ₂ O）₅ ] ⁴⁺离子。几项理论研究在未找到一致意见的情况下研究了有关水族离子的不同模型。这篇评论考虑了这些研究。由溶液产生的衍射产生键长，将键长与固态中已知几何形状和配位数的物质进行比较，并与不同的量子力学预测进行比较。总而言之，认为七坐标[Sc（OH2）7] ³⁺ 离子是溶液中发现的物质。