Question

Alkaline earth metal ions are more strongly hydrated than alkali metal ions

Answer 1

  Assuming you mean the number of water molecules associated with the ions, it's because the alkaline earth ions have a lot of unfilled orbitals in their outer shells and attact the available electron pairs on the oxygen in water to complete them. This is called coordination or complexation. Water is a fairly weak coordinating agent but will do in the absence of anything stronger. Stronger agents are ammonia, nitrate, chloride/ate, etc. Anything with electrons to share.

Answer 2

They have greater charge.alkaline earth metal ions have a +2 charge while alkali metal ions have +1 charge.alkaline metal ions have alot of unfilled orbitals in their outer shells and attract the available electron pairs on the oxygen in water to complete them.This is called coordination or complexion. Water is fairly weak coordinating agent but will do in the absence of anything stronger.