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| Thread ID: 57852 | 2005-05-14 10:02:00 | Why chlorine is a gas, bromine is a liquid while Iodine is a solid? | Renmoo (66) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 355102 | 2005-05-15 01:37:00 | They all have the same energy at the same room temp. It's just that Cl is lighter and so is more volatile. Br is heavier, is a liquid, and I is heavier still, and so is a solid etc. Well yes and no. Br has an atomic mass of 79.904 and is liquid at room temperature. Mercury (Hg) has an atomic mass of 200.59 and is liquid at room temp. But I has a mass of 126.9 and is solid. Go figure. I don't understand it. Each element has different numbers of electrons and protons so that the energy locked up differs from element to element. Destruction of Hydrogen would be spectacular but destruction of Bromine would be much more spectacular. Breaking the strong atomic force in Br would release enormous amounts of energy because there are more particles to break up than in simple H. But I'm being a bit unfair - Br and Hg are unique in being liquid given their weight. I agree that generally the heavier the element, the more likely it will be liquid or solid at room temp. There is not enough external energy to excite the heavier atoms to diffuse into a gas. |
Winston001 (3612) | ||
| 355103 | 2005-05-15 01:42:00 | It is explained here: www.chemguide.co.uk |
Terry Porritt (14) | ||
| 355104 | 2005-05-15 09:45:00 | Well yes and no. Br has an atomic mass of 79.904 and is liquid at room temperature. Mercury (Hg) has an atomic mass of 200.59 and is liquid at room temp. But I has a mass of 126.9 and is solid. Go figure. I don't understand it. Each element has different numbers of electrons and protons so that the energy locked up differs from element to element. Destruction of Hydrogen would be spectacular but destruction of Bromine would be much more spectacular. Breaking the strong atomic force in Br would release enormous amounts of energy because there are more particles to break up than in simple H. But I'm being a bit unfair - Br and Hg are unique in being liquid given their weight. I agree that generally the heavier the element, the more likely it will be liquid or solid at room temp. There is not enough external energy to excite the heavier atoms to diffuse into a gas. Water at less than 0% C is a solid = ice. Warm the water up enough it becomes a vapour = steam. In between it is a liquid. |
Elephant (599) | ||
| 355105 | 2005-05-15 13:23:00 | Well yes and no. Br has an atomic mass of 79.904 and is liquid at room temperature. Mercury (Hg) has an atomic mass of 200.59 and is liquid at room temp. But I has a mass of 126.9 and is solid. Go figure. I don't understand it. The reason that Hg is a liquid is because the atoms are so electron-dense, there is less attraction between the atomes to form a metallic crystal, despite their weight, and not really due to atomic mass per se. The atoms are too massive to form a gas though. |
vinref (6194) | ||
| 355106 | 2005-05-16 04:01:00 | All I can say is,heat won't pass from the cooler to the hotter,you can try but you had far better notter. | Cicero (40) | ||
| 355107 | 2005-05-16 05:31:00 | The reason that Hg is a liquid is because the atoms are so electron-dense, there is less attraction between the atomes to form a metallic crystal, despite their weight, and not really due to atomic mass per se. The atoms are too massive to form a gas though. None of that explains why Mercury is a liquid at room temperature, and of course it forms a gas, or metal vapour when heated to its boiling point. (That's how gold is extracted from crushed quartz, amalgam plus heat to vaporise the mercury and leave the gold behind) Lead is similar to Mercury in terms of atomic number, atomic weight, atomic radius, specific gravity, but is solid at room temperature. Mercury has a rhombohedral crystal structure, whereas Lead is cubic, but I don't know the significance of that on the physical properties. |
Terry Porritt (14) | ||
| 355108 | 2005-05-16 13:34:00 | None of that explains why Mercury is a liquid at room temperature, and of course it forms a gas, or metal vapour when heated to its boiling point. (That's how gold is extracted from crushed quartz, amalgam plus heat to vaporise the mercury and leave the gold behind) Lead is similar to Mercury in terms of atomic number, atomic weight, atomic radius, specific gravity, but is solid at room temperature. Mercury has a rhombohedral crystal structure, whereas Lead is cubic, but I don't know the significance of that on the physical properties. I found a site (www.du.edu) that explains it somewhat. I studied it in detail at Uni, but darn if I can remember anymore than this. Fermi levels are very vaguely familiar. |
vinref (6194) | ||
| 355109 | 2005-05-16 23:55:00 | That site uses the term 'binding energy' in a way that I'm not familiar with. To me atomic binding energy is the energy to remove electrons, and nuclear binding energy is the energy to split the nucleus up into neutrons, protons etc. They must mean the energy to break down the crystal lattice structure when the crystal melts. We studied basic theories of melting years ago at uni, using statistical mechanics, and the name Guggenheim comes to mind, but those theories go back to the 1930s, and would have been superceded by now, but they didn't go into detail for different elements, rather experimental melting points were used to determine constants and atomic frequencies for different elements in the derived formula. I suppose in the scale of temperature of physical phenomenon, the melting points of metals are all within 1500C or so, so it isn't surprising that some melt below or just above or the environmental temperature to which we attach great significance. Woods Metal, a eutectic of Bismuth, Cadmium, Lead and Tin melts at 70C, that is not far off room temperature, but it would be nice to know the reasons on an atomic scale for why different substances have different melting points. I'm sure there are uptodate solid state physicists out there who have all the answers at their finger tips :) |
Terry Porritt (14) | ||
| 355110 | 2005-05-17 01:48:00 | They don't call it "solid state" these days. It's Condensed matter now. Physics has degenerated since it was Natural Philosophy. :( Isaac had it right. |
Graham L (2) | ||
| 355111 | 2005-05-17 07:00:00 | From the reply of a Science teacher in www . studyit . org . nz (thanks Prescott! :thumbs: ), I now fully understood what happened . Chlorine, Bromine and Iodine all have a weak inter-molecular force between each molecule . To be more specific, this inter-molecular force is instantaneous dipole, also known as London force or dispersion force . As the amount of electrons increase in the molecules, there are more chances for the instantaneous dipole to happen as the chance of more electrons gather to one side increases . As such, Iodine, being the halogen that has the most electrons in it in comparison with Chlorine and Bromine, has a significant bigger inter-molecular force between its molecule, which results it exist as a solid rather than other states . Thanks for the reply everyone! Cheers :) |
Renmoo (66) | ||
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