The isotopes 252Cf and 251Cf.
The most important isotopes of californium are: Cf-252, Cg-249, Cf-250.
No. The most common isotope(s) of an element are often stable.
Californium (Cf) is an element in the actinide series who's most common use is in gold and silver prospecting.
Isotopes of a element are simply versions of that same element with different count of neutron, with that in mind they take all of the isotopes of a specific element and average them together taking in account the percent abundance of each so the most common isotope is the one on the periodic table.
The atomic number of californium is 98. The atomic mass of the most stable isotope - 251Cf - is (251) after IUPAC.
Tin or Stannum with 10 stable isotopes
The Most common isotopes of elements with 14 & 15 neutrons are, respectively, silicon & phosphorus.
It has 10
Hydrogen
Radioactive element of either Actinide/Lanthanide Series
Sodium is considered a monoisotopic chemical element - sodium-23; the isotopes sodium-22 and sodium-24 exist only in ultrtraces.
That sounds like hydrogen!