Berkelium is a synthetic, radioactive actinide metal first produced in 1949 at the University of California, Berkeley. It is typically obtained by neutron irradiation of americium or curium in nuclear reactors. The +3 oxidation state is most stable; +4 occurs in some compounds (e.g., BkO₂). Berkelium-249 targets were used to synthesize superheavy element 117 (tennessine).
Berkelium (Bk) is a man-made actinide with atomic number 97. It resides in the f-block (period 7), between curium (Cm) and californium (Cf). It was first identified in 1949 at the University of California, Berkeley—hence the name.
Berkelium is produced by neutron irradiation of lighter actinides (usually americium or curium) in high-flux reactors, followed by beta decays and radiochemical separations. A simplified schematic is:
\(\cdots \xrightarrow{(n,\gamma)} \mathrm{Am/Cm} \;\Rightarrow\; \text{(captures + \(\beta^-\))} \;\Rightarrow\; \mathrm{Bk\,isotopes}\)
Because yields are tiny, isolating microgram-scale quantities requires multi-stage solvent extraction and ion-exchange methods.
Bk(III) is dominant in aqueous chemistry and solid salts; Bk(IV) appears in some oxides and fluorides. Representative compounds:
A commonly cited ground-state configuration is [Rn] 5f9 7s2 (with some 6d/5f participation depending on chemical environment). The 5f electrons enable multiple oxidation states and rich coordination chemistry.
Notable examples:
The choice of isotope affects handling (decay heat, gamma emissions via daughters) and experimental applications.
Targets of \(^{249}\mathrm{Bk}\) were bombarded with calcium-48 to synthesize the superheavy element tennessine (Ts, Z=117). A stylized fusion reaction is:
\(^{249}\mathrm{Bk} + ^{48}\mathrm{Ca} \;\to\; ^{297}\mathrm{Ts}^{*} \;\to\; \text{evaporation residues + decay chain}\)
This showcased the role of transuranium targets in discovering new elements.
In water, Bk(III) predominates as hydrated ions such as \(\mathrm{[Bk(H_2O)_9]^{3+}}\). Under strongly oxidizing conditions, Bk(IV) can be stabilized in solids like BkO2, though true berkelyl (dioxo) species analogous to uranyl are not common.
Yes. Berkelium is a radiotoxic heavy metal. Principal hazards are internal exposure from inhalation/ingestion of particulates and decay heat from certain isotopes. Work requires licensed hot-cell or glove-box facilities, HEPA-filtered ventilation, contamination monitoring, dosimetry, and compliant waste management.
\(^{249}\mathrm{Bk}\) decays mainly by \(\beta^-\) to \(^{249}\mathrm{Cf}\):
\(^{249}\mathrm{Bk} \;\xrightarrow{\beta^-}\; ^{249}\mathrm{Cf} + e^- + \bar{\nu}_e\)
Successive \(\alpha\)/\(\beta\) steps lead toward long-lived actinides and eventually stable lead/bismuth isotopes.
Because of scarcity and radioactivity, berkelium is used almost exclusively in research (actinide bonding, separations, nuclear data). Its isotope \(^{249}\mathrm{Bk}\) has been pivotal as a target material for superheavy-element synthesis.