Can a compound be denser than it's densest element?

For the discussion of the sciences. Physics problems, chemistry equations, biology weirdness, it all goes here.

Moderators: gmalivuk, Moderators General, Prelates

Manabu
Posts: 30
Joined: Tue Nov 30, 2010 1:57 am UTC

Can a compound be denser than it's densest element?

Postby Manabu » Mon Nov 18, 2013 3:12 am UTC

Can a compound be denser than the densest element it is made from? I think that compound may end up lighter than the original elements, because it may form crystalline structures, and so on (real examples would be cool too). But can it end up denser?

A related question: is there something denser than Osmium at standard pressure/temperature conditions? We just don't know yet, or is it impossible? If possible, it must be a new element?

User avatar
Qaanol
The Cheshirest Catamount
Posts: 3060
Joined: Sat May 09, 2009 11:55 pm UTC

Re: Can a compound be denser than it's densest element?

Postby Qaanol » Mon Nov 18, 2013 3:50 am UTC

Is this homework?

Is there a material that makes up two thirds of your body, which is denser than any of its component elements?

Have you looked into alloys of osmium and iridium?
wee free kings

User avatar
PM 2Ring
Posts: 3653
Joined: Mon Jan 26, 2009 3:19 pm UTC
Location: Mid north coast, NSW, Australia

Re: Can a compound be denser than it's densest element?

Postby PM 2Ring » Mon Nov 18, 2013 4:53 am UTC

It is expected that hassium (element 108) and meitnerium (element 109), the elements below osmium and iridium in the periodic table, are very dense metals, but only a small number of atoms have been made of these elements. Of course, these elements are radioactive, with half-lives on the order of a few seconds, but that's quite long compared to most of the transuranics, and it's possible that hassium may possess a nuclear isomer that's a little more stable. Still, with the difficulties involved in synthesizing these elements and their short lives, it may never be practical to perform direct density measurements on them.

According to Wikipedia, hassium is expected to have a density of around 41 g/cm³ and meitnerium is expected to have
a density of around 37.4 g/cm³, which is significantly denser than osmium and iridium.

elasto
Posts: 3575
Joined: Mon May 10, 2010 1:53 am UTC

Re: Can a compound be denser than it's densest element?

Postby elasto » Mon Nov 18, 2013 5:02 am UTC

Qaanol wrote:Is there a material that makes up two thirds of your body, which is denser than any of its component elements?

Are you referring to water? A quick google shows water isn't denser than liquid oxygen.

(Maybe the OP meant at a given temperature and pressure though.)

User avatar
cyanyoshi
Posts: 389
Joined: Thu Sep 23, 2010 3:30 am UTC

Re: Can a compound be denser than it's densest element?

Postby cyanyoshi » Mon Nov 18, 2013 6:50 am UTC

If Wikipedia is to be believed, lots of ionic compounds are significantly denser than the elements they are composed of. As a random example, NaCl has a density of 2.16 g/cm^3, while Na and liquid Cl2 have respective densities of 0.97 g/cm^3 and 1.56 g/cm^3. This might be because the positively charged ions are smaller than their corresponding neutral atoms, and maybe also because the oppositely-charged ions are so strongly attracted to each other that they really squeeze together. I'm not aware of any stable substance that is denser than osmium at standard temperature and pressure, however. It would be pretty surprising to me if such a substance exists. (Disclaimer: I'm really not that knowledgeable about chemistry.)

stianhat
Posts: 175
Joined: Mon Jun 13, 2011 6:31 pm UTC

Re: Can a compound be denser than it's densest element?

Postby stianhat » Mon Nov 18, 2013 7:22 am UTC

All elements in the same whereabouts group-wise and lower than Ir and Os will be denser due to lanthanide and relativistic contraction continues. To the OP: yes, that is possible but it has to be a large size difference. Also, in most metals you can dissolve quite large amounts of hydrogen without any crystal dimension changes.

BeerBottle
Posts: 221
Joined: Thu Jan 17, 2008 5:26 pm UTC

Re: Can a compound be denser than it's densest element?

Postby BeerBottle » Mon Nov 18, 2013 2:40 pm UTC

Many gases will be more dense than their (gaseous) constituent elements at the same temperature and pressure. The ideal gas law tells us that for constant pressure and temperature, gasses take up pretty much the same volume per mole. Therefore if the volume is always the same, heavier molecules lead to more dense gas. Examples, N2O, NO2 are both more dense than either N2 or O2 at room temperature and atmospheric pressure.

Another way to do this is have a solid or liquid compound made only of gaseous elements. One example, water, has already been given. Others are NH3, XeF4. NCl3

User avatar
davidstarlingm
Posts: 1255
Joined: Mon Jun 01, 2009 4:33 am UTC

Re: Can a compound be denser than it's densest element?

Postby davidstarlingm » Mon Nov 18, 2013 5:09 pm UTC

Yeah, my mind jumped straight to water and other liquid/solid compounds which are composed only of gaseous elements.

Temperature and pressure should probably be specified to get a better answer.

Manabu
Posts: 30
Joined: Tue Nov 30, 2010 1:57 am UTC

Re: Can a compound be denser than it's densest element?

Postby Manabu » Tue Nov 19, 2013 2:49 am UTC

Thanks for the answers.

What I'm most interested is in the high end of the density scale, because those heavy elements are very rare, as they are hard to produce by stellar events, and tend to sink down away from the crust by earths gravity. And the heaviest ones are usually very unstable, radioactive, etc. I was wondering if we can produce denser materials from more widely available elements, likely at a lower cost. I asked for something that is stable at standard conditions of temperature and pressure (25°C, 1atm), but it may be produced at higher pressures, etc. For example, a diamond, except it has a density of only ~3kg/l. The material from a neutron star wouldn't fit, as I guess it wouldn't remain in that form if brought to earth... with terrible consequences for anything near it...

Neverthless, those facts about gases are interesting. And I've thought about water but forgot to write about it in my original post. And the alloys of iridium with osmium don't seem to possess any special density, as not much about them is written in wikipedia...


Return to “Science”

Who is online

Users browsing this forum: No registered users and 13 guests