Why hydroxides insoluble

Because the orbital is complete, and among other reasons, the first ionization will require more energy than the alkali metal in the same period. In addition to this, the second electron must then also be lost. This means that overall, it requires much more energy to ionize this group than the alkali metals. The solubility of the hydroxides of the metals lower in the alkaline earth metal group can be explained by the shielding effect , which effectively says that the ability of a positive nucleus to attract electrons decreases as the amount of orbitals surrounding the nucleus decrease.

The insolubility of the hydroxides of the transition metals can be explained both by the increasingly large ionization energies that result from successively removing electrons or negatively charged hydroxide molecules in this case from the metal cation, and the greater effective nuclear charge on the electrons across a period.

Solubility depends on complex interactions between many factors, but ionization and shielding aren't amongst them. IE and shielding have to do with how easily or likely you form the ionic compound at first place, and not how an ionic compound behaves after you make it.

In general solubility depends on Also, for dissolving ionic compounds in general, solvent molecules will experience a decrease in entropy as solvation shells of eg water molecules surround the ions in a particular orientation in order to form ion-dipole attractions. This effect is not too significant for group 1 ionic compounds. I'm not saying the above gives a complete story, but both factors above can both help explain the relatively high solubility of group-1 ionic compounds in general.

Sign up to join this community. The best answers are voted up and rise to the top. Solution As usual, we write the equilibrium equation so that we can write the concentration below the formula. Amphoteric Hydroxides Not all metal hydroxides behave the same way - that is precipitate as hydroxide solids. Questions Assume the pH of gastric juice to be 2. Calculate the pH of a 0. Give the value in M.

If not, find out what you need to know and then learn it. The Facts Solubility of the hydroxides The hydroxides become more soluble as you go down the Group. This is a trend which holds for the whole Group, and applies whichever set of data you choose. Some examples may help you to remember the trend: Magnesium hydroxide appears to be insoluble in water. Solubility of the sulphates The sulphates become less soluble as you go down the Group. Two common examples may help you to remember the trend: You are probably familiar with the reaction between magnesium and dilute sulphuric acid to give lots of hydrogen and a colourless solution of magnesium sulphate.

Solubility of the carbonates The carbonates tend to become less soluble as you go down the Group. There are no simple examples which might help you to remember the carbonate trend. What - no explanations? Questions to test your understanding I am not setting any questions on this page because it is so trivial. Ferrous hydroxide Fe OH 2 and ferric hydroxide Fe OH 3 are insoluble in water and form green colour and brown colour precipitates in water. These precipitates do not dissolve in excess aqueous NaOH.

Ammonium hydroxide is very well soluble in water. But its dissociation in water is partial incompleteness.

Magnesium hydroxide is not soluble when aqueous NaOH is added. Therefore Mg OH 2 cannot be an amphoteric metal hydroxide. You know, zinc hydroxide is an amphoteric hydroxide. But, magnesium hydroxide is not a amphoteric hydroxide. So we can see one white precipitate will dissolve when adding aqueous NaOH.

Some metal hydroxides are soluble and some are not.