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Utter bo**ocks, group one metals do not cause explosions in water bath tubs by 3cm burettes of substance /end rant
So, alkali metals, right...?
- Thread starter Dinomania
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I taught this to year 9s before xmas and that equation works for them all however mine weren't a high ability group and chemical symbols were a bit too much for them!
Caporegime
think we've all seen that video at school 
The question was whether the alkali metals from lithium to francium react according to the equation in the opening post.
)) can you give us some more detail?
The reaction is very favourable since the loss of the lone valence electron affords a noble gas configuration. It seems logical that increased reactivity corresponds to the rate at which the reaction proceeds; it might not be necessarily true that caesium has more energy to give out than lithium but it does so in a shorter timespan. Possibly for a couple of reasons the activation energy decreases on decending the group and for simplicity we could just consider the ionisation energy which decreases as that valence electron is, relatively speaking, much further away and less tightly held. Now, with an increase in reaction rate prescribed for a decrease in activation energy we can justify the observations.
In the interest of scienceeLbot said:
)) can you give us some more detail?I'm stating the obvious here, but this didn't seem to be the case in Vinni3's YouTube link. Lithium to potassium are less dense than water and thus float; rubidium and caesium are denser and would sink.Aod said:
Okay it's late but I don't think that even in layman's terms this provides a suitable answer as written. I got to see the demonstration for myself in year 9 but I don't recall the depth of the explanation and right now I can't think of how I would explain it without invoking electronic configurations.flibbage0 said:
The reaction is very favourable since the loss of the lone valence electron affords a noble gas configuration. It seems logical that increased reactivity corresponds to the rate at which the reaction proceeds; it might not be necessarily true that caesium has more energy to give out than lithium but it does so in a shorter timespan. Possibly for a couple of reasons the activation energy decreases on decending the group and for simplicity we could just consider the ionisation energy which decreases as that valence electron is, relatively speaking, much further away and less tightly held. Now, with an increase in reaction rate prescribed for a decrease in activation energy we can justify the observations.
As far as year 9 go it doesn't need to be in any depth really, they just need to know that a metal + water -> salt + hydrogen and then how to name the salt.
Soldato
think we've all seen that video at school
I'm showing my age now, if you've seen it too.
Soldato
I wouldn't refer to MOH as a salt, I'd reserve that for the product of reaction between a metal and a mineral acid.
On reflection what I wrote could be far beyond the scope of an introductory GCSE level class. The way the thread developed from a simple "is this right?" to offering explanations seems to me a bit like the Bad Translator thread where the input gets scrambled along the way
What would you say when one of the students asks why it's happening?
Soldato
I remember learning in Adv. Higher Chemistry that Francium is so rare and unstable that only something like 18 ATOMS of it are in existence on the planet at any one time!!!!
'Outside the laboratory, francium is extremely rare, with trace amounts found in uranium and thorium ores, where the isotope francium-223 continually forms and decays. As little as 20–30 g (one ounce) exists at any given time throughout the Earth's crust'
I do A2 chemistry at the moment so I think my explanation is valid enough.
flibbage0,
I wasn't questioning your credentials and I'd be surprised if you're the only member of the forum who's qualified to GSCE or AS level in combined science or Chemistry.
I only added I was of the opinion that, as written, attempting to explaining the increase in reactivity as being due to an increased number of shells, an increase in shielding and an increase in atomic radius tells the reader nothing about what reactivity fundamentally is. It's like it is just shy of telling you the immediate consequence of those factors, that's all.
I wasn't questioning your credentials and I'd be surprised if you're the only member of the forum who's qualified to GSCE or AS level in combined science or Chemistry.
I only added I was of the opinion that, as written, attempting to explaining the increase in reactivity as being due to an increased number of shells, an increase in shielding and an increase in atomic radius tells the reader nothing about what reactivity fundamentally is. It's like it is just shy of telling you the immediate consequence of those factors, that's all.