Need Help Finding a Service?
CLICK HERE - It's Free

Add Environmental
Yellow Pages
To Your Site

Business Center
Business Reviews
Free Directories
Upgrade Your Listing
Environmental Bids & RFP Services
Financing Available
Dust Collectors
Mist Eliminators
Ammonia Slip Analyzers
Chemiluminescence Analyzers
CO Analyzers
CO2 Analyzers
Flame Ionization Analyzers
HC Analyzers
Infrared Analyzers
Multi-Point Samplers
NOX Analyzers
Paramagnetic Analyzers
Photoacoustic Analyzers
Photoacoustic IR Analyzers
Process Control Analyzers
Tracer Gas Systems
VOC Analyzers
WMD Equipment
Air Monitoring
PID Rental
Water Quality
Water Sampling
NFPA Labels
Waste Labels
Flammable Labels
Lighting Equipment
Pumping Equipment
Cubic Yard Boxes
55 Gallon Drums
Hazardous Waste Drums
Overpack Drums
Plastic Drums
Submit Resume
View Resumes
Reports & Mapping
Tank Inspection Services
Mold & Mildew Info
Mold Franchise
Mold Test Kits
Mold Training
OSHA Training
EPA Training
Wetland Training
Water Wastewater
Grease Trap Bacteria
Pond Bacteria
Septic Tank Bacteria
* Celebrating our 22th year *
[ Home > Resources > Education > Periodic Table of the Elements ]

Proposed Name

Atomic Number: 105
Atomic Symbol: Db
Atomic Weight: 262
Electron Configuration: [Rn]7s25f146d3


In 1967 G.N. Flerov reported that a Soviet team working at the Joint Institute for Nuclear Research at Dubna may have produced a few atoms of 260-105 and 261-105 by bombarding 243Am with 22Ne. The evidence was based on time-coincidence measurements of alpha energies.

In 1970 Dubna scientists synthesized Element 105 and, by the end of April 1970, "had investigated all the types of decay of the new element and had determined its chemical properties," according to a report in 1970. The Soviet group had not proposed a name for 105. In late April 1970, it was announced that Ghiorso, Nurmia, Haris, K.A.Y. Eskola, and P.L. Eskola, working at the University of California at Berkeley, had positively identified element 105. The discovery was made by bombarding a target of 249Cf with a beam of 84 MeV nitrogen nuclei in the Heavy Ion Linear Accelerator (HILAC). When a 15N nuclear is absorbed by a 249Cf nucleus, four neutrons are emitted and a new atom of 260-105 with a half-life of 1.6 s is formed. While the first atoms of Element 105 are said to have been detected conclusively on March 5, 1970, there is evidence that Element 105 had been formed in Berkeley experiments a year earlier by the method described.

Ghiorso and his associates have attempted to confirm Soviet findings by more sophisticated methods without success. The Berkeley Group proposed the name hahnium -- after the late German scientist Otto Hahn (1879-1968) -- and symbol Ha.  However, the International Union of Pure and Applied Chemistry panel members in 1977 recommended that element 105 be named to Dubnium (symbol Db) after the site of the Joint Institute for Nuclear Research in Russia. Unfortunately, the name hahnium will not be used again according to the rules for naming new elements. Some scientists still use the earlier name of hahnium because it had been used for about 25 years.



In October 1971, it was announced that two new isotopes of element 105 were synthesized with the heavy ion linear accelerator by A. Ghiorso and co-workers a Berkeley. Element 261-105 was produced both by bombarding 250Cf with 15N and by bombarding 249Bk with 16O. The isotope emits 8.93-MeV alpha particles and decays to 257Lr with a half-life of about 1.8 s. Element 262-105 was produced by bombarding 249Bk with 18O. It emits 8.45 MeV alpha particles and decays to 258Lr with a half-life of about 40 s. Seven isotopes of element 105 (unnilpentium) are now recognized.