Final answer:
The white solid composed of sodium and iodine is a compound known as sodium iodide (NaI), which differs in properties from each element in its uncombined state.
Step-by-step explanation:
The homogeneous combination of sodium and iodine that forms a white solid is a compound known as sodium iodide (NaI). This substance is made up of sodium (Na) and iodine (I) in a fixed ratio, which is characteristic of a compound. Since it is a pure chemical substance that contains two or more elements chemically bonded together, it exhibits properties different from those of its constituent elements when they are separate.
A homogeneous mixture (also known as a solution) is one in which the components are evenly distributed throughout and cannot be visually distinguished from each other, whereas a heterogeneous mixture contains components that are not consistently distributed, so they can often be seen as individual substances. An example of a homogeneous mixture would be air, while sand mixed with pebbles would be a heterogeneous mixture.