Dissolution means to make the compound apart, So when we have ionic compounds like NaI which has metal and non-metal ions, It separates into parts of positive ions and negative ions. After we separate this compound apart we will put the charge of each on above its symbol and then start to balance the equation of the dissolution.
So the dissolution equation of NaI is:
NaI(s) → Na^+(s) + I^-(Aqu)
In science you want to use observations and measurements.
Below picture contains the given models.
Answer: Option-B is the correct model.
Explanation: Solid is a state of matter in which the particles are closely packed, has definite volume and shape. Like liquids they don't flow, either they occupy the volume of container as that occupied by both gases and liquids. The inter-molecular forces between solid particles are very strong as compared to liquids ans gases. So, the model B has a particles very closely packed to each other.