Any photos taken from Britannica ImageQuest do NOT have to be added to your bibliography. You must include this statement somewhere on your presentation: Unless otherwise cited all images are from Britannica Image Quest and are rights-cleared for educational use. You may still choose to have an informational caption under the photo.
Here are a few places that discuss elements within objects that you could use as a starting point for your project.
Here are a few resources that provide more information about chemistry, elements, compounds, and general sciences.
Here are a few resources relating to elements that are endangered.