Rutherfordium is a chemical element. It has also been named eka-hafnium and unnilquadium. It has the symbol Rf. It has the atomic number 104. It is a very radioactive element that does not exist in nature. It has to be made. Rutherfordium is the first transactinide element.. The isotope that has the longest half-life is Rf. Rutherfordium-265 only has a half life of about 13 hours.