What are transition elements?​

Transition elements are elements which have partially filled d-orbitals and form at least one or more stable ions.

Explanation:

it's transition state

which occurs in SN2 mechanism

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.

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )