h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

http://www.bbc.co.uk/h2g2/guide/A543575
This is a big one, please comment.

Cheers,

HELL

Hmm. First things first: Obvious typos:

Avrogadro example (I think this constant should be named by the way):

She adds the numbers and finds that he will need 209.4 grammes (grams?)
YOur chemist appears to change sex half way through this sentence.

How to use the periodic table of the elements (advanced) section, your example heading says Exapmle.

Group names: And here the group-names:
missing "are".



Other stuff: Could mention noble gases also often referred to as inert gases.


Apart from that, seems pretty good - nice ambitious entry choice .
Going back to read it again...

In name table, platinum is missing last 2 letters.

and Protactinium is missing a t.

Thanks vogonpoet,

mentioned typos have been corrected.
Avogadro included.
Chemist now has only one gender
example now reads example
missing "are" found and included
inert gases included

grammes are spelled correctly.

"one mole ore a few billions" should be "one mole or a few billions".

Actinoid should be Actinide

Lanthanoid should be Lanthanide

I don't like the way you abbreviate Periodic Table of the Elements to PTE and then use that throughout the article. I would prefer you to use the phrase "Periodic Table" wherever you have used PTE.


A great article. Good work!

Geezus...

Protactinium and Platinum are now correct

I SWEAR I wrote them correctly...

Tanks vogonpoet.

My encyclopaedia lists Avogadro's number as 6.023 x 10^23. It is nice the way the 23 occurs in both parts of the number.

OK I'll replace PTE w/ Periodic Table... (but not right now, maybe someone likes it)

Then:

Gnomon, 6.02209E23 is the Avogadro number, your encyclopaedia rounded the number wrongly.

Lanthanoids and Actinoids is the currently official designation of these groups. Lanthanides and Actinides could be confusing if you have Laves-Phases (weird Alloys) containing a Lanthanoid with a negative charge (THAT would be a Lanthanide - ide is the termination for the salts of the corresponding hydric acid) So IUPAC figured out that they didn't want to use Lanthanides and Actinides any longer...

Thanks Gnomon, keep in touch...

HELL

Hi good stuff

A few comments

Maybe you should mention that the atomic weights are in amu (atomic mass units based on Carbon-12 being 12).
Also I've never seen the rare earths described as lanthanoids - lanthanides is the term I've always used although I guess this depends on which textbook you look in. Similarly actinides not actinoids.
In the first paragraph of 'More Detailed information you write instable rather than unstable).
Your comment is not really correct about elements above uranium BTW. Plutonium is available in quite large quantities - just don't tell any terrorists and you can buy Americium - we used it at school as I recall for doing radioactivity experiments in A level physics.
Electronegativity is far from fuzzily defined, there are extremely precise calculations and experiments done to measure these. The model they use to define them maybe a bit fuzzy however, and I'm sure most people's understanding of this quantity is highly fuzzy
Do the nobel gases really not have an electronegativity. Certainly Krypton and Xenon can form compounds (maybe argon too by now) and so must have electron affinities.

This footnote I do not like at all:

7 NaBr dissolves well in water, if a silver nitrate (AgNO3) solution is added, eventually the Ag and Br ions will come close enough and temporarily built the AgBr compound (silver bromide). This compound is not well soluble in water, it will precipitate. Why? The bromine atom is not electronegative enough to completely retain the electron from the silver (it is also on the right side of the table), both atoms will have to share it, they will not form ions which are easily dissolved in water.

This is not at all correct I'm afraid

Whether something is ionic or not has no bearing on solublity - whether a compound is soluble or not has to do with whether the hydration energy of the ions exceeds the lattice energy of the solid crystal. Ethanol is a good example of something that is not ionic at all and still dissolves in water. silver bromide is *not* molecular which is waht your footnote says. It is ionic but there is a grey area between truly ionic such as sodium chloride and the formation of molecular orbitals - silver bromide shows some tendencies of both. Barium Sulphate is an excellent example of an ionic salt that is totally insoluble in water.

I must say I've never heard of any group names for groups three four and five, these names seem highly contrived - they seem to have simply been given names for the sake of it because the other groups have. That's not your fault though


Also, wouldn't it be nice to mention which elements are metallic, non-metallic and metalloidal in character?
You might want to mention that many elements have multiple isotopes too

Orcus

Ah, from your previous post I see that IUPAC have been at it again. Try finding a working chemist who *actually* calls them lanthanoids - and noone who uses the damn things would get confused - if they did then they are too stupid to be doing research science. Still, if IUPAC have spoken then you are right to write Lanthanoid and Actinoid.
IUPAC deal too much in semantics sometimes for my liking. I seriously doubt its energetically possibel to generate a compound with a negative rare-earth ion in it outside of a physical chemist's vacuum chamber/laser construction so this is really a bit pedantic of them.

OK Orcus. Here we go....

1: Weights in amu... OK good idea

2: Electronegativity: Pauling's? Mulliken's? What is the square root of an energy? Thermodynamic Electronegativity? Kinetic? I too am a chemist, and I admit feeling comfortable with electonegativities, they are a extremely practical concept. But they do not have anything in common with reality. (It's like saying electrons are yellow, or blue.) From a physical point of view the electronegativity (and unfortunately also the affinity) vary from case to case... sp3 carbon has a different ENtivity as sp2 carbon and sp1. The EN and EA(Affinity) vary from molecule to molecule, just because of the tiny differences in conformation. I think it IS definetely FUZZY. You cannot say C has an EN of 2.55 period. because it can be 2.0 or 7.9 depending on whatever. For me this IS fuzzy.

3: Solubility part: OK you are right. I just stepped down and wanted to make an example for laymen. I'll try to redo this part (Maybe you have a good suggestion?)

4: Pentels and Triels... It's like you said. Sometimes you find them in literature though.

5: Right: NOONE uses Lanthanoids and Actinoids... But IUPAC is IUPAC. About the possibility of generating negatively charged rare-earth ions: Are you familiar with Laves and Hume-Rothery Phases? They are used to describe Alloys... It's theoretical crap if you ask me... But hey, give them inorganic guys a chance.

6: Isotopes... I'll include a brief comment.

7: Metallic Non-Metallic and Metalloid. Maybe it should be added, but maybe it is too much. I do not want to overload the table. I'll work on it.

Thanks orcus. I got the message. Working on it.

HELL

Fair enough, you kind of make my point though, there has been an awful lot of work done on electronegativities and I'm sure a bunch of metrologists would probably have a fit if they heard the definitions being described as fuzzy.

Annoying metrologists is though, so go for it .

I still think you should mention that some of the Noble gases are not in fact inert though.

BTW, it is a good article - just trying to help

Ah Oh Yes, and about Plutonium and Americuim... You can also buy Technetium. Just because you can buy something it does not mean it is not artificial. (I'll change the available as traces part for that purpose)

In Nature ONLY Th, Pa and U exist (OK: negligible traces of Np and Pu due to natural Nuclear reactions in U-Ores if you want to be pedantic) But that's it. All others are man-made.
cf.Hyde, Perlman, Seaborg "Man-made transuranium elements" Prentice-Hall 1964. (Probably in any good general Chemistry book you will find similar entries)

By the way.. Did you know that Th is as abundant as B on this planet? And that there is more U than Au?

Cheers...

HELL

If you want a suggestion on the ionic thing, why not just say that elements of similar electronegativity, when combined, tend to share electrons and form molecules and elements of highly different electronegativity tend to swap electrons with one another and form ionic salts?

Or words to that effect.

I was only taking issue with the comment about there only being a few atoms existing. This is true of something like Lawrencium or Francium but when something is availabel to buy by schools, even if it is artificial then there are still more than a few atoms of it.
This depends on your definition of "a few" mind. If you count a number as large as 6*10^23 as "a few" then fine

Oh and one other thing - I looked the new elements up a few weeks ago and did you know they hit a magic mountain? Apparently they made 1 atom(???!!!!) of element 115 and it had a half life of milliseconds -remarkably stable in comparison to the microsecond half lives of the preceding nuclides .

Milliseconds? Really? I would quite like to read about that.
Oh, and I guess I would call then Lanthinoids and Actinoids - I am currently studying chemistry at edinburgh (Spending 4th yr in german uni though), and our lecturer (after a few ascerbic comments about IUPAC ) used the 'oids version.


Oh, and wouldnt it be simpler and less fuzzy to mention that there are many different ways of measuring/definig electron negativity, as opposed to just saying fuzzy?

Just do a web search for periodic tables, some have links to details of the individual elements, that's how I found it

Incidentally, I could have sworn I read somewhere on some unit conventions web page that both grams and grammes were acceptable spelling, but a quick glance round the web just seems to confirm that most people are as ignorant as I am . Lots of pages seem to use both grams and grammes.