what is an atom

,,what is an element ,,

who is smaller and bigger

,, what is the relation between them?

For getting solutions to all the questions kindly ask a single question in one link. We have answered the first two question and the rest will be answered once you post them in different threads.
Kindly refer to the following link:- 
https://www.meritnation.com/ask-answer/question/what-is-an-atom/atoms-and-molecules/3418140   
https://www.meritnation.com/ask-answer/question/what-is-element/elements-and-compounds/5071876