Q:  How many hydrogen atoms are there for every single carbon atom?

        The ratio is

          N (hydrogen)        (12 - 8.5)
         --------------  =  10                 =  approx 3,200 
          N (carbon)


  Q:  Do you notice a pattern in these abundances?  Can you explain it?


         Elements with even atomic numbers (even numbers of protons)
         are more common than those with odd atomic numbers.
         Apparently, nuclei with an even number of protons are slightly
         more stable than those with an odd number of protons;
         so, when these elements were fused in the cores of stars,
         the even-numbered elements were produced in larger quantities.


  Q:  Why is the value for hydrogen set to 12?

         It's just a convenience: if the log10(abundance) of hydrogen
         is set to 12, then the log10(abundances) of almost all the other
         elements remain positive.