Had a skim, this seems relevant [0] > The Na+ hydration shell, which is formed by three water molecules, is quite stable while the K+ ion can only perturb the

Had a skim, this seems relevant [0] > The Na+ hydration shell, which is formed by three water molecules, is quite stable while the K+ ion can only perturb the water structure in its immediate neighborhood so that it is unable to attract the water molecules. As a result the diameter of the hydrated Na+ is about 0.5 nm while the K+ diameter is equal to its ionic diameter. Basically in water Na+ and Cl- are surrounded by water molecules attracted by electrostatic forces. This will add bulk to the naked ion and they are reasonably stable/robust You can get an intro into solvation shells here[1] [0] https://www.sciencedirect.com/science/article/pii/0005272896000199#:~:text=As%20a%20result%20the%20diameter,equal%20to%20its%20ionic%20diameter https://www.sciencedirect.com/science/article/pii/0005272896.... [1] https://en.m.wikipedia.org/wiki/Solvation_shell https://en.m.wikipedia.org/wiki/Solvation_shell