>>11431243You start out with pure hydrogen and helium
General downward trend is direct result of needing more hydrogen and helium to make heavier elements
Iron is higher than others because it's the end point of normal fusion, meaning moving into either direction from there costs energy.
Some of the light elements (Li - B) are lot lower because they readily fuse into carbon much easier than helium fuses into them
Starting from carbon the oscillation with every other element being more abundant comes from the fact that lot of fusion happens with helium so Silicon fuses with Helium directly into Sulfur leaving Phosporous at lower abundance and so on.
See:
https://en.wikipedia.org/wiki/Stellar_nucleosynthesishttps://en.wikipedia.org/wiki/Abundance_of_the_chemical_elementsFor further reading
Also probably homework
