Which of the following elements are in order of decreasing atomic radii (size)? A. Cu, Br, Zn

B. He, Ne, Ar

C. Li, Si, Ca

D. Al, Ga, In

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.

they are all solids.