How much do elements weigh?

[blutoski]

Just a point upon which I will, as a physics teacher, nitpick... please refer to the quantity in question as the atomic or molecular mass, not the weight. You wouldn't believe how hard it is to undo the misconception that mass & weight are equivalent when students get to physics after having had chemistry.

duly noted

 

[MattusMaximus]

duly noted

Many thanks

 

[shadron]

Well, I didn't actually have a question, but you've now prompted one: What, exactly, is your point?

Hmmmmm..... Well, maybe I'm just suffering a senior moment. Let's see......Nope, there it is:

I'm just intrugued to know why you [Rat] assumed that a guy [Mojo?] who seems to be versed in where and how to erect a building should be qualified to comment on atomic physics! Tip: If you ever need a dripping tap fixing suggest you don't waste your time calling a florist!

Now, I was responding to your implied question to Rat as to why he accepted what Mojo said about physics. I may have been a bit out of line doing that since I wasn't the one addressed, but I also replied to Rat before I read your question, so I thought I would respond by saying in my usual pedantic and circumlocutious style that lots of people know lots of things, and if we were all limited to speaking on those topics we were degreed in the forum would be a dry place. It seems pretty clear to me what my point was. Agree or disagree as you want, but if you pose a question don't be surprised when I respond to it.

 

[Olowkow]

Totally correct. He mw = 4.00. So helium gas has about half the buoyancy of hydrogen gas.

That's what happens when I throw everything into excel, fire out a bunch of results mechanically, and skip the 'reality test' step before posting.

Not quite so:
http://en.wikipedia.org/wiki/Lighter_than_air

Thus hydrogen's additional buoyancy compared to helium is:

• 1.202 / 1.113 = 1.080, or approximately 8.0%

Thus helium is almost twice as dense as hydrogen. However, buoyancy depends upon the difference of the densities (ρgas) - (ρair) rather than upon their ratios. Thus the difference in buoyancies is about 8%, as seen from the buoyancy equation:

 

[jimbob]

Indeed, the atomic masses will tell you how much mass an element will have, the molecular masses will be the how much mass each molecule of a compound will have and chemistry will tell you which compounds are feasible.

The periodic table will help you interpret how elements will react together, and whether they are going to be solid, liquids or gases.

The further to the left or down, the more metallic.

Why this is, boils down to quantum mechanics. But a simple explaination can be that electons 'want' to fill "shells" that contain even numbers of electrons, and that more electrons can fit into later shells, so there can be 2 electrons in the first shell, (hence two elements in the first line: Hydrogen and Helium) then 8* then 8** then...
The inner electrons "shield" the outer electrons slightly from the nucleus, meaning that it is easier to lose electrons with higher atomic numbers, metals lose electrons more easily whilst non-metals gain electrons more easily)

The further to the left of the periodic table, the easier to lose electrons to make a full shell, to the right it is easier to gain electrons to make a full shell. Ionic compounds (salts) have a metal "donating" electrons and a non-metal receiving electrons. These compunds (eg Sodium Chloride) are stuck in a crystal lattice of positive (metal) and negative non-metal) ions, which attract each other and so are very solid.

Nonmetals can "share" electrons (covalent bonding) but these tend to be isolated Cl₂ is two chlorine atoms sharing one pair of electrons to "fill" their shells. This is a gas.




So top right: most reactive non-metal (Florine) (it is so reactive that it can even react with the "inert" Xenon, which is the least unreactive of the "inert elements").

Bottom-left: most reactive metal (Francium)
*Li, Be (metals) B (metallic and non-metallc properties), C(a nonmetal, but some metallic properties) , N( non-metals), O, F, then Neon (full shell, inert)

**Na, Mg, (metals) Al (some non-metallic properties but a metal, Si (semiconductor), P(non-metals), S, Cl, then Ar (full shell, inert)
for the derali about qualifications: I a semiconductor engineer, with a physics background mainly working on device physics, but with the odd bit of processing too (so moderatly rusty A-level chemistry)

 

[Olowkow]

Not sure what this gas would be, (Xenon?) but if you've never seen the film, it is pretty neat:
http://www.youtube.com/watch?v=UvgMlY3SyP0

 

[shadron]

Not sure what this gas would be, (Xenon?) but if you've never seen the film, it is pretty neat:
http://www.youtube.com/watch?v=UvgMlY3SyP0

More likely Halon. It has the specific property of being rather dense, the better to smother electrical fires. And it's probably a great deal cheaper.

 

[Madalch]

Not sure what this gas would be, (Xenon?) but if you've never seen the film, it is pretty neat:
http://www.youtube.com/watch?v=UvgMlY3SyP0

Sulphur hexafluoride, I think, is the usual gas for this kind of demonstration.

I doubt they'd use xenon, since it has an odd effect on people- it's actually a mild narcotic.

 

[robinson]

Xenon is an anaesthetic?

http://bmb.oxfordjournals.org/cgi/content/full/71/1/115#SEC6

Wow. All the nobel gases have anesthetic properties. The stuff you can learn on these forums. How cool is that.

Comparing environmental issues between Xenon and Nitrous:

Nitrous oxide is 230 times more potent as a greenhouse gas than carbon dioxide, taking 120 years to break down. The amount of nitrous oxide released as an anesthetic contributes 0.1% of the greenhouse effect.

Goto T. Is there a future for xenon anesthesia?/Le xenon a-t-il un avenir en anesthesie? Can. J. Anaesth., 49, 335–8.

 

[Olowkow]

Sulphur hexafluoride, I think, is the usual gas for this kind of demonstration.

I doubt they'd use xenon, since it has an odd effect on people- it's actually a mild narcotic.

Interesting about xenon, and its use as an anesthetic.
Sulphur hexafluroide sounds right to me, non toxic and:

colorless, odorless gas
Density 6.164 g/L, gas phase at 1 bar
(~5.1 times denser than air)
1.329 kg/L, liquid phase at 25 °C
2,510 kg/m3 or 2.510 kg/L, solid phase at −50.8 °C

 

[Southwind17]

Hmmmmm..... Well, maybe I'm just suffering a senior moment. Let's see......Nope, there it is:

Now, I was responding to your implied question to Rat as to why he accepted what Mojo said about physics. I may have been a bit out of line doing that since I wasn't the one addressed, but I also replied to Rat before I read your question, so I thought I would respond by saying in my usual pedantic and circumlocutious style that lots of people know lots of things, and if we were all limited to speaking on those topics we were degreed in the forum would be a dry place. It seems pretty clear to me what my point was. Agree or disagree as you want, but if you pose a question don't be surprised when I respond to it.

Nope, I think you were correct first time around: senior moment. The quest for knowledge:

I'm just intrugued to know ...

is neither a question nor an implied question.

I don't disagree that:

... lots of people know lots of things ...

and that:

... if we were all limited to speaking on those topics we were degreed in the forum would be a dry place.

but I'm not at all surprised that a guy who seems to be "degreed" in:

... building regs and planning stuff

doesn't have a very good grasp of chemistry. He could have completely flunked at chemistry and still be a top building control officer, town planner or the like (in fact, he probably did!).

No, as you yourself suggested, I'd also be inclined to put your impulsiveness largely down to your "usual pedantic and circumlocutious style".

 

[shadron]

Nope, I think you were correct first time around: senior moment. The quest for knowledge:

I'm just intrugued to know ...

is neither a question nor an implied question.

As you will, South. Whatever.