Why is there a zig-zag in elemental abundances? In this answer to Is lithium considered a metal in astronomy? this image from Wikimedia of the abundances of elements in the universe was shared:

Credit: Wikimedia Commons user 28bytes, under C.C.-by-S.A.-3.0.
I thought it was fascinating that there is a near-constant zig-zag of abundancies.
Are these values accurate, and if so, what would cause this zig-zag?
Nuclei are more stable if they have an even number of protons Z, and are also more stable if they have an even number of neutrons N. This is because the particles form pairs. (Almost all nuclei with both N and Z odd are unstable with respect to beta decay.)
If a nucleus is going to have significant cosmic abundance, it must be either absolutely stable or at least have an extremely long half-life. This is more likely to happen when Z is even (and also when N is even).
Stability also effects probabilities of different types of decay. E.g., if a nucleus can undergo both beta+ and beta- decay, then it is usually more likely to do the decay that results in the more stable daughter.