Francium is an extremely rare, highly radioactive alkali metal. The most stable isotope is Fr-223 with a half-life of about 22 minutes.
The ground-state electron configuration of francium is [Rn] 7s1, placing it in Group 1 with the alkali metals. Like Cs and Rb, the single valence electron makes Fr strongly reducing and extremely reactive (in principle) toward water and halogens.
Francium almost exclusively exhibits the +1 oxidation state, forming ionic compounds such as francium chloride (FrCl) and francium hydroxide (FrOH) in analogy with other alkali metals.
All francium isotopes are highly radioactive with short half-lives. The most stable, \(^{223}\mathrm{Fr}\), has a half-life of only about 22 minutes. Any francium produced in natural decay chains quickly decays, so only trace amounts exist in uranium/thorium minerals at any moment.
Francium occurs as a transient product in several natural decay series (e.g., from actinium/uranium chains). A representative decay for the longest-lived isotope is:
\(\mathrm{^{223}Fr \xrightarrow{\beta^-} \,^{223}Ra}\)
Other isotopes may decay via alpha emission, continuing the chains toward stable lead isotopes.
Francium was discovered in 1939 by Marguerite Perey at the Curie Institute. She named it after France. Before confirmation, it had been tentatively called "eka-cesium" based on periodic trends.
Only in theory or at the single-atom scale. Bulk reactions have not been observed due to extreme radioactivity and scarcity. By analogy, it would react violently with water and halogens:
\(\mathrm{2\,Fr(s) + 2\,H_2O(l) \rightarrow 2\,FrOH(aq) + H_2(g)}\)
\(\mathrm{2\,Fr(s) + Cl_2(g) \rightarrow 2\,FrCl(s)}\)
In practice, any sample decays before macroscopic chemistry can be performed.
No practical commercial uses exist. Francium’s short half-life, intense radioactivity, and scarcity limit it to fundamental research (e.g., atomic structure, laser cooling of single atoms, precision tests of parity violation).
Because gram-scale samples cannot be accumulated, most values are estimated or extrapolated from periodic trends. Francium is expected to be a soft, very low-melting metal (similar to or lower than Cs) with high density and a body-centered cubic structure—yet direct bulk measurements are lacking.
Francium isotopes can be synthesized by nuclear reactions (e.g., heavy-ion bombardment of gold or thorium targets) and then isolated as single atoms in magnetic/optical traps for spectroscopy. A stylized example reaction is:
\(\mathrm{^{197}Au + ^{18}O \;\rightarrow\; ^{210}Fr + 5\,n}\)
Specific channels depend on beam energy and target.
Yes. Francium is highly radiotoxic. Even picogram quantities emit significant radiation. Work with Fr is restricted to specialized facilities; single-atom experiments employ remote handling, shielding, and ultra-high vacuum/laser apparatus to minimize exposure.