[Titanscape (OP)]

How reactive is Francium in water and air, firey...?

Titanscape

[Ultima]

I saw a video of it... make that explosive! [] (with water, I imagine it just crusts over in air....?)

wOw the world spins?

[chris]

It's at the bottom of group 1 and hence is a large atom with a loosely bound single outer electron. Hence it's very reactive.

I'm not sure you can obtain it in sufficiently large quantities (not least because of the price) to do any very impressive experiments like reacting it with water !

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Ultima]

Hmmm it might have been Cesium or something else I saw on video... But if Francium is more reactive than that... []

http://fr.physics.sunysb.edu/francium_news/frconten.htm

wOw the world spins?

[Kryptid]

Francium probably is more immediately reactive with water than caesium is. This is because francium likely has a lower melting point than cesium, so it will be melted by the heat of its reaction with water more quickly. This is what causes alkali metals to become more reactive down the periodic table. In the gaseous state, it is just the opposite. Lithium is the most reactive, and things get less reactive from then on.

[daveshorts]

I seem to remember talking to a chemist a few years ago who said that Francium was not as reactive as Cesium, because the electrons are starting to move so fast that relativity significantly alters the properties of the atom, so it stops following the pattern of the group.

According to http://www.hull.ac.uk/php/chsajb/heavy_ho/5dmetals.html a Francium atom is smaller than a Cesium one due to relativistic effects, so this may well be the case. Apparently it also explains why gold is so unreactive.

[neilep]

This is interesting....besides being ' fuel ' for questions on this site what have I to thank Francium for in my everyday life ?



Men are the same as women.... just inside out !!

[daveshorts]

I think that the reason that there are no videos is that it is extreemly radioactive and the longest half life isotope has a half life of about 22 minutes, so it doesn't hang around long enough to do many experiments on.

Having a look at www.webelements.com it would appear that the ionisation energy of Ceasium is lower than Francium although Francium is apparently slightly more electronegative - I think we really need a chemist to decrypt this

[rosy]

quote:it would appear that the ionisation energy of Ceasium is lower than Francium although Francium is apparently slightly more electronegative

To a first approximation those two are the same thing... a low ionisation energy means that it's easy to remove an electron. So the element must be less electronegative (less keen to hang onto its electrons).
Electronegativity's not exactly a physical measurable anyway, it's more of a concept which helps chemists to consider how elements will react... there are loads of ways of calculating it which give slightly different values.

[gerard]

anyone know where i can get my hands on a video of above reactions?

[epeius]

it is  believed that due to its highly reactive nature that only seven francium atoms exist on the earth at any one time... i dont think were going to be seeing a video anytime soon.....

[daveshorts]

quote:Originally posted by epeius

it is  believed that due to its highly reactive nature that only seven francium atoms exist on the earth at any one time... i dont think were going to be seeing a video anytime soon.....

I think by reactive you mean radioactive, but yes

[stinkinstudentlamo]

Francium is so reactive (and radioactive) that it was only discovered theoretically. it is only formed with the radioactive decay of actinium.
the image is a sample from the notebook of Margurerite Perey, the discoverer of Francium, who was an assistant to Marie Curey.


I refuse to answer that question on the grounds that I don't know the answer.
-- Douglas Adams

[Mjhavok]

I did some reading on Marie and Pierre Curie and the discovery of Pollonium and Radium. She was a very humble woman. Not seeking fame or wealth.

Steven

[Quantum_Vaccuum]

ur not gonna get a francium vidion, and anyway, there are aprox. 22 grams of francium on earth at once, not 7 atoms.

[DrDick]

You should be suspicious of those references that say that the properties francium is somehow anomalous compared to the other alkali metals.  Given that the half-life is so short, it's difficult to perform experiments on francium (as has been mentioned before).  Here's some data from a book that I have ("The Elements", by John Emsley, pub. 1987)

Element   First ionization energy   atomic radius
Cs              375.7 kJ/mol            265.4 pm
Fr              400 kJ/mol              c. 270 pm

Be careful with zeroes.  They often are a result of rounding.  To me, as a scientist, these numbers may mean 400 +/- 100 kJ/mol and 270 +/- 10 pm (because of significant figures).

In a more recent book ("Chemistry of the Elements", by Greenwood & Earnshaw, pub. 1997), I find the following values:

Element   First ionization energy   atomic radius
Cs              375.7 kJ/mol            265.4 pm
Fr              ~375 kJ/mol            not listed

You can see a further refinement of the ionization energy, but it's still approximate.

It is possible to have an element smaller than the one above it, but this is because of well-understood contractions (e.g., Hf < Zr because of the immediately preceding addition of f-block elements, the Lanthanides).  This discontinuity tends to happen right after a new block (Ga is not smaller than Al, but isn't as much larger as we would normally think).

Dick

[Quantum_Vaccuum]

Don't they freeze it in some kind of beam to lengthin its life, to make it studiable?

[Bored chemist]

There are no videos of francium. 22 grams on the whole earth isn't a lot. 7 atoms in a lab is about enough to get a reasonable measurement of the half life. I doubt that its ionisation potential,  hydration energy or practically anything else have ever been measured- they might have been calculated. I always like to point out that mathematical models like those used for that sort of calculation are similar to those used in weather forecasting.

"Don't they freeze it in some kind of beam to lengthin its life, to make it studiable?"
Unfortunately, that sort of thing only works on star trek, there's not a lot can be done about nuclear instability.

[Quantum_Vaccuum]

We study francium by cooling and trapping it in a magneto-optical trap, and then subjecting it to a variety of laser pulses. We trap francium by neutralizing on a piece of heated yttrium and injecting it into a magneto-optical trap (MOT). The MOT is formed at the intersection of six laser beams shining through a glass cell vacuum chamber and an anti-Hemlholtz magnetic field, as depicted in the above apparatus figure.

   We use the MOT because it allows us to trap the francium in vacuum with no substrate in a volume less than 1 mm wide. The MOT also cools the trapped francium to below 100 µK, reducing the Doppler shift and broadening of spectroscopic lines to negligible levels.

   In 1995, the Francium Spectroscopy Group trapped 3,000 francium atoms in a MOT for the first time. In 2002, after redesigning and rebuilding the apparatus, the group succeeded in trapping francium with peak MOT populations of over 200,000 atoms, and an average MOT population of 50,000 atoms.

--http://saaubi.people.wm.edu/ResearchGroup/Research/Francium_Research/Francium_Introduction.html

So what exactly would that mean?

[Bored chemist]

It means they took some francium, vapourised it and trapped the vapour in a vacuum chamber by, in effect, squashing it between a set of laser beams.
It's still just as unstable there as it is anywhere else (3.2 min half life, same as always) but OK I stand corrected, they did some spectroscopy on it. (I doubt they measured a hydration energy)
Probably the most impressive bit of that is that they got hold of 200,000 atoms of the stuff at any one time. Thanks for pointing this out; it's an interesting piece of science.