Final answer:
Supergiants form heavier elements than red giants due to the much greater pressure and temperatures in their cores. Red giants can create elements like carbon and oxygen, whereas supergiants can synthesis elements heavier than iron, especially during supernova explosions.
Step-by-step explanation:
Red giants and supergiants differ substantially in terms of the elements they can produce. Red giants, which are lower-mass stars, are capable of producing elements like carbon and oxygen during their helium-burning phase. However, they are not able to produce the heavier elements found within our planet such as silicon and iron, nor the elements like gold and silver used in jewelry. These heavier elements require much more extreme conditions than those present in red giants.
On the other hand, massive stars that evolve into supergiants do have the potential to fuse elements into heavier ones. This is due to the much greater pressure and temperature in their cores compared to red giants. Supergiants can expand to an enormous size and experience dramatic mass loss, which contributes to the synthesis of these heavier elements. Ultimately, it is in the centers of more massive red giant stars, and even more so during a supernova explosion, where elements up to and beyond iron (on the periodic table) can be formed. Therefore, supergiants have the capability to form a wider variety of elements, including those heavier than iron.