While the elements are the individual components of a design such as line, colour etc. The principles are the way in which these elements are brought together.
Format: The shape of the image
Ground: everything that is not the main subject of the image
Harmony and Unity
Movement and Motion
Download the notes on this here
I have also provided a video in two parts you can watch that might provide more information. The approach taken is a bit different to the notes, but this just goes to show that opinions vary on the devinitions of terms in this area, and the general principles are what is important.
Once you have studied all the information modify the mind map you produced for the elements section of work with this new information. No need to start afresh, just update and edit your previous work. e.g.
I will collect this mind map to look at on Friday of this week.