2 - Carbon and Its CompoundsOnline version Chapter 10, Lesson 3: "Carbon and Its Elements" Click the "Show Clue" button to read the hint and answer on the line. by Naneth Burquez 1 These elements are formed when carbon bonds with itself. Hints 1 One of these elements can be used in jewelry. 2 One of these elements is the hardest naturally occurring material known. 3 One of these elements can be used to write with (pencils have it).