Dubnium is a synthetic, highly radioactive transactinide in group 5. It is produced in particle accelerators in trace amounts; no bulk samples exist, so most physical data are predicted rather than measured.
Dubnium (Db) is a synthetic transactinide with atomic number 105. It belongs to Group 5 (the vanadium family), below vanadium (V), niobium (Nb), and tantalum (Ta), and lies in period 7.
Dubnium atoms are created via heavy-ion fusion reactions in particle accelerators by bombarding actinide targets with lighter ions, then rapidly separating the products. A stylized example is:
\(^{249}\mathrm{Bk}(^{18}\mathrm{O},\,xn)\,^{267\text{–}x}\mathrm{Db}\)
Only a few atoms are formed per experiment, which then decay within seconds to minutes.
Newly formed Db atoms recoil out of the target and are carried to detectors. Scientists identify them by their time-correlated decay chains (mostly \(\alpha\) decays and sometimes spontaneous fission) and the characteristic energies of emitted particles.
\(^{A}\mathrm{Db} \;\to\; ^{A-4}\mathrm{Lr} + \alpha \;\to\; \cdots\)
By analogy with Group-5 congeners, +5 is expected to be the dominant oxidation state for Db, with possible access to +4 under reducing conditions. Gas-phase and chromatography studies at the single-atom level suggest formation of halides and oxychlorides similar to Nb and Ta (e.g., pentahalides and mixed oxy-species under chlorinating conditions).
Relativistic calculations indicate a ground-state configuration close to [Rn] 5f14 6d3 7s2. Participation of the 6d and 7s electrons, together with relativistic effects, is expected to drive Group-5-like chemistry.
Because only atom-scale quantities are produced and they decay quickly, it is not currently possible to prepare macroscopic samples. Therefore, properties such as melting point, boiling point, crystal structure, and density are predicted from trends and atom-at-a-time experiments rather than measured directly.
Most characterized Db isotopes undergo alpha decay and, in some cases, spontaneous fission. A generic \(\alpha\)-decay step can be written as:
\(^{A}_{105}\mathrm{Db} \;\to\; ^{A-4}_{103}\mathrm{Lr} + \alpha\)
Half-lives are generally in the range of milliseconds to minutes, depending on the isotope.
Early studies indicate Db behaves as a Group-5 transition metal, showing chemical trends similar to Nb and Ta in halide formation and complexation. However, relativistic effects in the 6d series may produce subtle deviations from simple periodic trends.
Yes. Dubnium is a radiotoxic element, but experiments use only a few atoms at a time. Work is performed in highly specialized facilities with remote handling, rapid transport systems, shielding, and rigorous radiological controls.
One illustrative route is:
\(^{243}\mathrm{Am}(^{22}\mathrm{Ne},\,4n)\,^{261}\mathrm{Db}\)
Here, the compound nucleus formed by \(^{243}\mathrm{Am}+^{22}\mathrm{Ne}\) emits n neutrons (evaporation) to reach a Db isotope that is then tracked via its decay chain.