Questions

[Scienuk]

Hello,

1. Considering the fact that the formation of bonds releases energy, do stronger bonds release greater energy than weaker bonds, hence why the greater the charge and the smaller the atomic radius the greater the magnitude of the lattice enthalpy?

2. What type of bond is formed during hydration such as when NaCl dissolves in water and the ions are separated from the crystalline lattice by the partially charged atoms in the water molecule, what type of bond is formed between the ions and water molecules?

[kw0573]

1) Yes, formation of stronger bonds release greater energy. Electric forces are stronger when the charges are packed tightly, which takes more external energy to separate compared to when the charges are packed loosely. Conversely, when a bond is formed, the molecule now releases the same amount of energy that was required as input to break the same bond.
2) When an ionic compound dissolves in water, there cease to be a bond between the ions. Instead there form ion-dipole forces, which are a type of intermolecular forces. When NaCl dissolves in water, the Na⁺ bonds to the O in several water molecules, and the Cl^- bond to the H in several other water molecules. 

Edited May 26, 2016 by kw0573

[Msj Chem]

The smaller the ionic radius, the closer the ions can get to each other which results in a stronger electrostatic between the oppositely charged ions (and a stronger bond). The greater charge on the ion also results in a stronger electrostatic attraction between the oppositely charged ions ( and a stronger bond). If you are considering lattice enthalpy, it will have a positive value (endothermic) when (one mole of) ionic compound is broken up to form gaseous ions and a negative value (exothermic) when the ionic compound is formed from its gaseous ions. 

This video may help: