So, alkali metals, right...?

Dinomania

Dinomania

Dinomania

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2 M (s) + 2 H2O (l) ? 2 MOH (aq) + H2 (g)

If M is the chemical symbol for the element in Group 1 of the periodic table (lithium, sodium, potassium, rubidium, caesium, francium), do they ALL follow the same pattern?

Obligatory 'fun bit':
(PS. Yes I know apparently the explosions are falsified - still fun though)
 
They should all follow the same pattern, but they get very rare and very expensive as you go further down. They also get more reactive as far as I know.
 
Seen a science video rubidium, it is indeed explosive. tiny bit shattered the petri dish. They also did caesium and it did indeed explode and blew the petri dish to tiny pieces.
 
Yes, they get more reactive.

I know most of the basics, and I'm teaching it on Monday (physics is my specialism rather than chemistry) - however I can't find any specific reference to the reactions of Rubidium, Caesium and Francium (which is, yes, incredibly rare and radioactive, if you manage to get enough to clump together, it just disintegrates anyway).

No chemists here?
 
I remember at school some guys raided the science store and took the entire stock of sodium and went and dumped it in a toilet and legged it. Blew the toilet to bits, the stall door off it's hinges into the sinks opposite and the entire wing had to be evacuated.
 
Yeah, all alkali metals will follow the pattern you described above. The main change is just the reactivity; the reactivity increases down the group, hence the explosion you see from the biggest ones.
 
In my chemistry classroom at school one of the wooden cupboards at the back had lots of little holes about an inch deep in it from when some students pinched a huge chunk of sodium and dropped it into a water bath, with predictably explosive results.
 
DAnDan said:
Yeah, all alkali metals will follow the pattern you described above. The main change is just the reactivity; the reactivity increases down the group, hence the explosion you see from the biggest ones.
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Except in real life it turns out that there are a lot of factors involved. That's why the tests were faked: because actually it turns out that sodium produces the biggest explosion, so that had to use explosive charges to help the higher elements in the table.


M
 
Meridian said:
Except in real life it turns out that there are a lot of factors involved. That's why the tests were faked: because actually it turns out that sodium produces the biggest explosion, so that had to use explosive charges to help the higher elements in the table.


M
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Fair enough, first I've heard of that! Got any links to any papers or anything? Will be an interesting read!
 
Meridian said:
Except in real life it turns out that there are a lot of factors involved. That's why the tests were faked: because actually it turns out that sodium produces the biggest explosion, so that had to use explosive charges to help the higher elements in the table.


M
Click to expand...

We saw Lithium and Sodium reacting with water in school and were shown a video of Potassium. The potassium reaction was more than twice as powerful as the sodium reaction, and managed to put a crack in the glass beaker.
 
Sorry for the rather late reply.

What level of education are we pitching this towards? I ask as I don't want to over-complicate the answer and/or spend ages typing out explanations that may be a little far flung. GCSE? AS/A2?

The answer is unfortunately both yes and no depending on what level we're discussing this at.
 
The Caesium explosion was actually quite correct.

I've got a tin full of sodium (in oil) in the garage). Had some right laughs with it. I had a set up where I had a big inverted funnel over the top of a bucket of water. Drop a large piece of sodium down the funnel and place objects on the funnel spout. Eventually the object would get blown about a hundred feet or more straight up in the air. :D
 
Year 9s, it's just an introduction to the elements and the periodic table, but they're quite high-ability.

Lithium, Sodium then Potassium are fairly linear in reactivity as I put them into water last Tuesday! Potassium looks great as the heat it generates is enough to light the hydrogen it's giving off in the reaction with water - nice whizzbang effect!

Rubidium and Caesium I've never handled or thrown into water - there's a famous video that shows Caesium breaking the water bowl - however someone reckoned they may have faked it by using acid instead of water to make the reaction quite so explosive.

As I understand it - Caesium and Rubidium ARE chemically more reactive - but they give off so much Hydrogen that they bounce off the water on a cloud of gas instead of hanging around and fizzbanging.
 
sara said:
As I understand it - Caesium and Rubidium ARE chemically more reactive - but they give off so much Hydrogen that they bounce off the water on a cloud of gas instead of hanging around and fizzbanging.
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yep. the reaction is so quick and powerful that the metal is completely surrounded by bubbles of gas allowing the sample to react quite slowly, actually.
 
Francium only exists for a few seconds (if that) at any given time, and only a tiny amount exists.

The reason why they get more reactive is because as you go down group 1 in the periodic table, the number of shells increases and so does the shielding and atomic radius also increases.
 
flibbage0 said:
Francium only exists for a few seconds (if that) at any given time, and only a tiny amount exists.

The reason why they get more reactive is because as you go down group 1 in the periodic table, the number of shells increases and so does the shielding and atomic radius also increases.
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yep. it's estimated that there's only about four or five grammes of francium on earth at any one moment in time.
 
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