There are several things to consider before determining which will be less stable and which will be more stable:
1. Opposite charges attract, i.e. a positive charge will be attracted to a negative charge. Therefore, those crystals that have two equal charges will repel each other and will be less stable. As in the case of figure B, this will be the least stable of all, number 4. The rest of the figures have a negative charge followed by an intercalated positive charge.
2. The charges of the ions are also very important, we see in Figure C, a larger charge of ions. While in the other figures the size is +1 or -1, in figure C we see a value of -2 or +2, therefore the force of attraction will be greater and will be more stable. Figure C will be the most stable of all and will have the number 1.
3. Last but not least the size of the molecule and the distance between them will affect the force of attraction. The larger the molecule and the greater the distance between them, the less attractive force it will have. Figure D shows molecules of larger size and greater distance between them, therefore, it will be less stable than figure A. So the order will be:
1. C
2. A
3. D
4. B