In which process does a solid change directly into a vapor?
(1) condensation (3) deposition
(2) sublimation (4) solidification

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

increased stability in the completion of fluorine's outer shell.