A certain metal M crystallizes in a lattice described by a face-centered cubic (fcc) unit cell. The lattice constant a has been measured by X-ray crystallography to be 526.pm. Calculate the radius of an atom of M. Be sure your answer has the correct number of significant digits, and be sure it has the correct unit symbol.

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.

if you're asking what comes out, it's steam.