There are three naturally occurring isotopes of hydrogen. study the table of isotopic information below. name of hydrogen isotope symbol description protium 1h the most common isotope of hydrogen deuterium 2h can combine with oxygen to form a compound known as "heavy water" tritium 3h low-level radioactive isotope that is often used to trace hydrogen-containing molecules in scientific experiments which isotope contains the greatest number of protons? a. tritium b. they all contain the same number of protons. c. deuterium d. protium