Final answer:
Medium-sized stars can fuse elements up to carbon in their cores during their lifecycle. They cannot produce heavier elements because they lack the necessary core temperature and pressure, unlike massive stars that can fuse elements up to iron
Step-by-step explanation:
The highest element that medium-sized stars can fuse in their core during their lifecycle is carbon. Unlike massive stars, medium-sized stars, which are typically less than 2 solar masses, do not have the core temperature or pressure necessary to fuse elements heavier than carbon. As a result, they cannot reach the conditions required for the fusion of elements such as oxygen, neon, magnesium, and silicon. For massive stars, on the other hand, the process of nuclear fusion can continue until they start producing iron in their cores. However, the fusion of iron consumes energy rather than releasing it, leading to the star's eventual demise.
In the earlier stages of their evolution, medium-sized stars can fuse hydrogen into helium. After exhausting their helium, through the triple-alpha process, they form carbon (and sometimes a bit of oxygen). Once helium fusion is no longer viable, these stars lack the capability to ignite further fusion of heavier elements due to insufficient core temperatures and pressures. Consequently, for medium-sized stars, carbon marks the end point of their nucleosynthetic capabilities, and further fusion does not occur within their cores.