Describe how nuclear fusion and other processes in stars have led to the formation of all the other chemical elements.

Nuclear fusion is the process in which smaller nuclei fuse together to form larger nuclei. An example is the process of nuclear fusion that place in our Sun. Here, hydrogen nuclei fuse together to form helium nuclei. It is believed that the Big Bang (which is the most widely accepted model of the origin of our universe) itself created light elements such as hydrogen, helium, lithium, beryllium, etc. These lighter elements fuse to form heavier elements, up to iron. For a significant fraction of its life, a star generates energy by fusing hydrogen to helium. During its later years (and depending on its mass), fusion may create other elements. Helium fuses to form carbon in many stars. In case of heavier stars, oxygen and other elements (such as magnesium, silicon, etc.) are also formed. These reactions are exothermic. However, formations of heavier elements, beyond iron, are generally endothermic processes (they require energy input). These elements (trans-iron) were formed when a star went supernova. This is the phase in the life cycle of a star when the outer expanding layer of a star is thrown out. This explosion generates enough energy to fuse elements and form trans-iron elements. 

Such processes have formed 92 naturally occurring elements. The rest of the elements are man-made and have short lives.

Hope this helps.