Dubnium is discovered in 1967 by both workers at a Nuclear Institute at Dubna, near Moscow Russia and at the University of California in Berkeley, USA. Each team created the element using *Particle Accelerators but with different elements. The team from Berkeley created the element by bombarding 249Cf with 15N nuclei and the team from Dubna created it by bombarding 243Am with 22Ne ions. Dubnium is named after the town Dubna in Russia. The Nuclear Institute at Dubna main objective is to seek for heavy elements such as Dubnium.
The reason why there are two elements for this element:
Ever sense the element has been discovered there has been a dispute over the name of the element between the two groups of scientists who discovered it. The project was a mutual effort between a group of scientist from the Joint Institute for Nuclear Research at Dubna, in Russia and a group from the University of California at Berkeley. After the element was discovered, the group from Russia named the element Dubnium, from the town Dubna. But the group from Berkeley wanted to name the element after Otto Hahn, the German Chemist who discovered nuclear fission, Hahnium.
Because of the overwhelming evidence from the Berkeley team gave in their method of making the element, it was named Hahnium. But in 1997, the International Union of Pure and Applied Chemistry changed the name from Hahnium to Dubnium, the reason is unknown. But I think the reason why they changed it is because Dubnium sounds better ^_^
* Particle Accelerators are machines that are made to make small particles such as protons and atoms move at an extremely high velocity; at times they reach the speed of light which is 186,000 miles per hour (300,000,000 meters per second). The particles are forced to smash into atoms, and if done correctly they will stick to the atom, making it heavier. For example the making of Dubnium.
The Particle Accelerators cost millions of dollars making them rare, most of them are located in the US in some collages; Lawrence Berkeley Laboratory at the University of California at Berkeley. There is on located in the Join Institute of Nuclear Research, in Dubna, Russia. Another one is in the Institute for Heavy Ion Research in Darmstadt, Germany.