Dubnium
Dubnium is a chemical element. It has the symbol Db and it has the atomic number 105. It is a very radioactive element that does not exist in nature. It has to be made in a lab. It is a transuranium element created by bombarding californium-249 with nitrogen-15 nuclei. The isotope that has the longest half-life only has a half life of 32 hours. Dubnium is a transactinide element.