Starting with hydrogen, in what order do elements undergo fission on the sun?

I think you mean, in what order do elements undergo fusion
on the sun.  Fission occurs when larger elements, such as uranium, split into smaller
elements and release one or more sub-atomic particles such as neutrons, in the
process.

Fusion is the joining together of two small
elements to form a new larger element.  The primary fusion process on the sun is the
combining of two hydrogen atoms to form an atom of
helium.

On stars like our sun, the only fusion reactions
are hydrogen combining to form helium.

On stars that are
bigger than the sun, additional fusion reactions can take place. In turn, helium and
hydrogen can combine to form lithium.  Two helium can combine to form berylium and so
on. This process can continue until iron (element 26) is formed.