Re: If it began with Hydrogen what will it end with.

Dear Peter,

I'm assuming from your question that you mean the creation of the 
elements, beginning with hydrogen...."Where will the creation of the 
elements end and into what will they decay?" As it turns out, all the 
elements have decay paths.  What are known as the "radioactive elements" 
decay to lighter elements relatively "quickly" (seconds-to-100,000 years).
The other elements will also decay, but on longer timescales of 10^33(1 
with 33 zeros after it) years and by different physical processes, such 
as nucleon decay (decay of the protons within the elements) into quarks.  
See this URL for mor info...

=> http://hep.bu.edu/~superk/pdk.html

Astronomers have studied how elements heavier than iron were produced in 
the early Milky Way have identified a distinct series of epochs of galaxy-
wide chemical formation. Looking at hundreds of stars in the oldest part 
of the Milky Way – the “halo” region around the center - they have 
developed a timeline to explain their observations:


The Pre-Stellar Epoch 

The Big Bang jumpstarts the initial large-scale production of hydrogen, 
deuterium, helium and lithium.

The Epoch of Very Massive Stars 

The earliest stages of heavy element formation in the Galaxy were 
dominated by stars with masses ten times that of the Sun or more, and 
lifetimes of a few million years or less. These supermassive stars 
produced small amounts of all the elements, but their presence can be 
identified most clearly by excesses of elements like strontium, yttrium 
and zirconium. Released by supernovae and absorbed by new star-forming 
clouds, these elements were incorporated into the next generation of 
stars.

The Europium Epoch 

For the next 30-100 million years, element formation was dominated by 
supernovae from stars with about 8-10 times the mass of the Sun. These 
longer-lived stars enriched the Milky Way in heavier elements like 
barium, europium, and other lanthanide elements in the Periodic Table, 
such as cerium.

The Double Shell Epoch 

A major shift from previous epochs, lasting from about 100 million to a 
billion years after the Galaxy formed, it featured stars with perhaps 3-7 
times the mass of the Sun. These stars produced more strontium, barium, 
and some particular lanthanides from nuclear-burning interior shells 
during the later stages of their evolution, not by supernovae. Their 
products are characterized by more solar-like distribution of heavy 
elements.

The Iron Epoch 

From one billion to three billion years after the Galaxy formed, 
supernovae from white dwarf stars a bit larger than the Sun produced 
large amounts of iron. The addition of large amounts of iron to the Milky 
Way's chemical stew can be deduced by the relative decrease of heavier 
metals within stars which hold about 1/100th of the Sun's overall metal 
abundance.

Since this epoch, which ended roughly 10 billion years ago, the major 
edition to the Galaxy's inventory of heavy elements has been lithium.

This timeline may be a surprise. The evolutionary path taken by stars is 
not a straight-line creation of lighter-to-heavier elements.  In fact, 
most of the heavier elements in the Milky Way Galaxy were formed 2-3 
billions years ago, while today lighter element production seems to 
dominate. 

So, to answer your question, the evidence to date seems to indicate that 
we will not see the creation of any heavier elements than now exist 
naturally, or are created by humans artificially…unless there is a future 
epoch in stellar evolution we do not forsee.

A useful URL is…

=> http://calspace.ucsd.edu/virtualmuseum/ita/03_2.shtml
 
Hope this helps answer your question(s)!

---* Dr. Ken Beck