Radiometric methods gave better results. After the radioactive decay series of ²³⁵U, ²³⁸U and ²³²Th with stable lead as end-products had been studied, it was assumed that radioisotopes of element 87 exist as intermediate members of these decay series. As early as 1914, Meyer, Hessand Paneth studied a carefully purified ²²⁷Ac preparation and observed a-particleswith a range of 3.5cm, which they attributed to element 87. 

In 1939, Mme. Marguerite Perey, of the Curie Institute in Paris, thoroughly studied a-particlesof the same range in the decay of a radioactive ²²⁷Ac sample,and found a daughter b^--active decay product with T_1/2=21 min. The chemical properties of thisproduct were close to those of caesium. Thus, for example, the b^--activity remained completely in the filtrate after precipitation of BaCO₃, lead and bismuth sulphides and lanthanum hydroxide and fluorides, but passed quantitively into a caesium prechlorate precipitate. It was thus establishedthat this is an isotope of element 87 with mass 223. This isotope was originally designated as "Actinium-K" (Ac-K), along with other decay products of actinium.

In 1946, Mlle. Perey termed this element francium (in honour of her native France) and in 1949, the IUC (International Union of Chemists) adopted this name and assigned the symbol Fr to the new element. 

Of the first 101 chemical elements, francium is the most unstable. The closest to it is astatine (At), which has a maximum T_1/2 = 8½ hours.
 

The appearance of the comparatively long-lived²¹²Fr amongst the shorter-lived francium isotopes is not accidental,but is a logical consequence of the regular properties of the a-active isotopes of heavier elements according to which the value of Eain the isotopes of one element increases linearly with decrease in massnumber A. This dependence departs from linearity only near nuclei thathave a filled shell of 126 neutrons; q.v. Fig 1. 

The existence of a francium isotope witha neutron number of 125 (equating to ²¹²Fr) was assumed, with Ea minimalcompared to the neighboring isotopes. This isotope was found in the productsof thorium irradiated by 350MeV protons. ²¹²Fr with Ea approx. = 6.4 MeV and T_1/2 =19.3 minutes was found in 1950. The main source for the preparation ofthis isotope is products of the fission of Th and U by high energy protons.

The cross-sections of formation of thefrancium isotopes £220 during the fissioning of uranium nuclei by 660 MeV protons have been calculated (Fig 2), and ²²⁰Fr should have the maximum yield (just under 10 mbarns). The cross-section of ²¹²Fris comparatively low, at 0.2 mbarns. When thorium nuclei are fissioned,the cross-section of formation of ²¹²Fr should be higher. Ahigher yield of ²¹²Fr is attained in the reaction ¹⁹⁷Au(²²Ne;a,3n)Fr²¹².The decay scheme of ²¹²Fr is shown in Fig 3.

In accordance with the pattern of a-decaythe isotopes with a neutron number (N) of 128 have the shortest half-lifeand the highest Ea.²¹⁵Fr is such an isotope (Fig 1). The twojuxtaposed isotopes ²¹⁴Fr and ²¹⁶Fr are also short-livedcompared to isotopes with A £213 and A ³217. For isotopes with A between 215 and 221, function Eais linear, Fig 1; hence, the half-lives also increase.The isotope ²²²Fr is the lightest b^--activity francium isotope. 

An almost complete list of knownisotopes (there are allegedly 34 as at 2000) with their associated atomic weights and half-lives is shown in Fig 4.  N (thenumber of neutrons) may be obtained by subtracting 87 from the isotopenumber, #.  

In this table:
ec denotes electron capture (wherean electron is caught, the upshot of which is that a proton changes intoa neutron, thus changing the atom into an element with Z equal to one less,ie, Radon (86) in Francium's (87) case). The value of A remains constant,as the net effect of losing a proton and gaining a neutron is zero.
a denotes alpha decay; here, a helium nucleus (2 protons, 2 neutrons) is ejectedfrom the francium nucleus, leaving an atom with Z equal to two less, ie,Astatine (85).  This is because the number of protons dictates what element an atom is.  The value of A decreases by four (2 protons +2 neutrons).
b denotesbeta decay; here, a neutron decays into an electron and proton.  Theupshot here is that Z increases by one (Radium (88)) as there is now onemore proton in the nucleus and the electron is ejected, and it is this electron that is detected as the beta radiation. The value of A remainsconstant, as the net effect of losing a neutron and gaining a proton is zero.

Note that different sources state different numbers of isotopes; I shall try and list as many as I can glean from thosesources.  In any case, the only 'natural' isotope of Francium found in nature is ²²³Fr which is part of the actinium decay series. ²²¹Fr is part of the neptunium decay series, but this tends not to be 'natural'. 
 

# A T1/2 Decayprocess 201 201 0.048s a®197At 202 202 0.34s a®198At 203 203 0.55s a®199At 204 204 2.1s a®200At 205 205 3.9s a®201At 206 206 16s a®202At 207 207 14.8s a®203At 208 208 59s a®204At;ec®208Rn 209 209 50s a®205At;ec®209Rn 210 209.9964 3m 12 s a®206At;ec®210Rn 211 210.99553 3m 6 s a®207At;ec®211Rn 212 211.99618 20m a®208At;ec®212Rn 213 212.99617 34.6s a®209At;ec®213Rn 214 213.99895 5.1x 10-3 s a®210At 215 215.00033 1.2x 10-7 s a®211At

# A T1/2 Decayprocess 216 216.00319 7x 10-7s a®212At;ec®216Rn 217 217.00462 2.2x 10-5 s a®213At 218 218.00756 7x 10-7 s a®214At 219 219.00924 21s a®215At 220 220.01231 27.4s a®216At 221 221.01425 4m 54 s a®217At 222 222.01754 14m 24 s a®218At 223 223.01973 21m 48s a®219At;b+®223Ra 224 224.02323 2m 42s b-®224Ra 225 225.02561 3m 54 s b-®225Ra 226 226.0293 48s b-®226Ra 227 227.0318 2m 24s b-®227Ra 228 228 39s b-®228Ra 229 229 50s b-®229Ra

All the isotopes with masses ³215 were obtained by fissioning U or Th nuclei with fast particles. The cross-sections of formation of these isotopes are between 1 and 7 mbarnswhen U is fissioned with 660 MeV protons.

The isotope ²²³Fr has been themost exhaustively studied. Its decay scheme is shown in fig 5. Possiblea-decay of ²²³Fr with an energy of 5.5 ± 0.2 MeV was predicted from the empirical laws for a-activeisotopes; the probability is between 6 x 10^-4 and 4 x 10^-5of the b^--decay. By means of high-speed photographic plates, a-particles with an energy of 5.38 ± 0.08 MeV were observed in the decay of²²³Fr. The ratio a/bwas 6 x 10^-5. 

²²⁷Ac is the main source of²²³Fr, formed as the result of the a-decay of ²²⁷Ac; the a-decay is 1.2% of the b^--decay.The ²²⁷Ac preparations are obtained either by the waste productsof the uranium industry or by irradiating ²²⁶Ra in a nuclearreactor by the reaction: 

Note that the reported number (and details) of francium isotopes varies greatly with source, hence the caveat on the number of actual isotopes that exist or have been created.
 

 

²²⁷Ac¾®0.2 mg
²²³Fr¾®3.8 x 10^-10g (0.17 mCurieor 4.65 x 10⁶ dpm)

²²¹Fr¾®1.0 x 10^-17g / tonne of natural uranium

In the earth's crust as a whole, at anygiven time there is probably only 25 - 30g of francium. This amount is, of course, distributed throughout the crust and represents the amount in equilibrium with its host ore. As can be seen from the above figures, the amount in any one place is miniscule. As such, it competes only with astatine for the accolade of being the rarest of the 92 naturally-occurring elements.

No weighable amounts of francium have ever been produced, nor are ever likely to be, due to its extreme transient nature. Radiometric studies of francium have been undertaken with samples of the order 10^-9 g in weight.
 

²²³Fr has been usedin limited biological research. In the study of the distribution of Fr, Rb and Cs in different organs of rats, it was found that the alkali metals accumulate chiefly in the kidneys, liver and salivary glands. It was shown that Fr is also fixed in an experimentally-induced sarcoma. Increase in the activity of Fr in the affected tissue appears immediately after onsetof growth. This diagnostic method for cancerous diseases could be promising as there is no [little?] damage to the organism because of the short lifetime of either ²²³Fr or ²¹²Fr.

Apart from these applications, there is no commercial application of francium, due to its transient nature.
 

Boiling point -> 677ºC (950 K)

Francium, in the same way as other alkalimetals, has no tendency to form complexes or colloids. The adsorptionalproperties of Fr⁺ have not been studied because of the shortlife of its isotopes. 

In analogy to Cs⁺, whose adsorptionon glass, Teflon and polyethylene has been studied in detail, it can beassumed that the adsorption of Fr⁺ on these surfaces from aqueoussolutions at pH 4 thru 11 will be insignificant. It has also been provedthat the adsorption of ¹³⁷Cs on a polypropylene surface is considerablyless than on glass or Pyrex. It would appear that francium has similarproperties.

In contrast to many artificial elements(Pu, Np, Tc, Pm et al), francium cannot ever be obtained in weighable amountsdue to there being no long-lived isotopes thereof. Hence, all the chemical and physical properties of francium have been studied with extremely low amounts, typically £10^-15g. Given its position in the Periodic Table, francium is expected to be the most electropositive element, continuing the procession down the Group 1 line from Li to Cs. Francium exists in just one oxidationstate, +1. Data on analysis of francium suggest that it is a complete analogue of Rb and Cs; in other words, many of its properties can be inferred from properties of those two elements. As time goes on, these properties are duly verified. The chloride, nitrate, sulfate, fluoride, sulfide, hydroxide, carbonate, acetate and oxalate of francium would be readily soluble in water, but the perchlorate, picrate, iodate, and some salts (such as Fr₉Bi₂I₉)would be sparingly soluble.

According to its position, francium should have a more negative standard potential than caesium (where E₀= -3.04 V). Therefore, francium can be separated on mercury only. However,very dilute amalgams are unstable; amalgams formed from 10^-9M 137Cs show this. Attempts to obtain similar results for 10^-14M francium were unsuccessful even when ultra-pure reagents were used. The francium amalgam decomposes a few minutes after the current isturned off. The amount of francium that passes into mercury at a given potential is less than that of caesium; this proves that francium is separated at a more negative potential than caesium.
 

The problem of separating francium from other alkali elements frequently arises in the analysis of products ofdifferent nuclear reactions. In the analysis of natural objects ²²⁷Acis separated from the main components and then from its decay products.²²³Fr is separated from ²²⁷Ac after radioactive equilibriumhas been established, typically about 2 hours.

There are several documented ways to extractfrancium; these include extraction, sublimation and ion exchange. Theseprocesses are far too detailed to go into here, but the book in the biblographydetails them. However, a lab at Stony Brook has perfected a technique tocapture 10,000 francium atoms at once. For more information, check outtheir link.
 

"Analytical Chemistry of Technetium,Promethium, Astatine and Francium".

by A.K.Lavrukhina and A.A.Pozdnyakon, AnnArbor-Humphrey Science Publishers Inc., 1970. Other information gleanedfrom reference works and own research.
 

• Web Elements is an excellentPeriodic Table resource on the web, and has been recently updated.
• The Stony Brook reference detailsan experiment whereby 10,000 Francium atoms are trapped with the use oflasers. 

This page is now complete! I would onlyneed to add extra information as it comes along, such as more isotopes.Keep checking back for the latest update. Some weird format changes occurred 23 Aug 2011 when I was able to restore the background image and the other images on the page - these I will fix in due time (mainly words got joined together).