Why are hydroxides of earth alkaline metals are so insoluble in water?

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SUMMARY

The insolubility of hydroxides of Earth alkaline metals in water is primarily due to the strong ionic bonding between the alkaline metal cations and hydroxyl ions. For instance, magnesium hydroxide (Mg(OH)2) exhibits a low solubility of only 1.4 mg/100ml, despite being a polar compound capable of hydrogen bonding. The ionic bonds are significantly stronger than the interactions with water, which limits their solubility compared to alkali metal hydroxides.

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  • Understanding of ionic bonding and its strength
  • Knowledge of polar compounds and hydrogen bonding
  • Familiarity with the properties of Earth alkaline metals
  • Basic chemistry concepts regarding solubility
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  • Research the solubility trends of alkaline earth metal hydroxides
  • Study the differences between ionic bonding in alkaline and alkali metals
  • Explore the concept of ionic radii and its effect on solubility
  • Learn about the role of dipole interactions in solubility
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jaumzaum
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Why are hydroxides of Earth alkaline metals so insoluble in water?
They are polar compounds and have an OH group, so they should do hydrogen bounds with water, as well as permanent dipole interactions, which in my conception are strong forces.
Even Mg(OH)2, witch do not have a big mass, has a solubility of just 1,4 mg/100ml
Can anyone help me to understand this?
 
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jaumzaum said:
They are polar compounds and have an OH group, so they should do hydrogen bounds with water, as well as permanent dipole interactions, which in my conception are strong forces.

Yes, but the ionic bonding between a alkaline oxide metal with two positive charges and a hydroxyl ion are even stronger (more than twice as strong as in a corresponding alkali metal given that the ionic radii are smaller, too).
 

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