Why is there an abundance of even atomic number elements vs odd ones?

The answer is (drum roll please):

Helium Burning

Basically, once particles cooled to actually form nuclei, a quick chain of nuclear (fusion) reactions occured:


The following reactions the occured:

etc etc...

Thus, as helium reacted with other, primarily even numbered nucleii, the even numbered elements showed an increase in abundance compared to the odd elements.

Note: Iron (26Fe) is the most stable of elements, hence it's greater abundance compared to surrounding elements.