Why is mercury a liquid even though its atoms are closely packed

In summary, the density of ice is less than that of water because of its hexagonal lattice structure, while the density of mercury is more than that of many solids due to its strongly bonded outer electrons. The state of a substance is determined by its crystal structure, which is influenced by bond angles and chemical nature of the bonds. Mercury is a liquid because its outer electrons are not easily available for bonding, making it a softer metal. The noble gases remain gases due to their full outer shells, and mercury gas behaves similarly to a noble gas with single atoms.
  • #1
jablonsky27
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the density of ice(solid) is less than that of water(liquid) and density of mercury(liquid) is more than that of many solids.
thinking about it, it seemed natural to me that the more closely are the atoms or molecules packed the greater will be their density. but on packing them closely, isn't the state also going to be more solid-like?
so what determines a substances density and what determines its state?
what keeps the H20 molecules in place in ice but not as tightly packed as in liquid water so that its density is reduced? and why is mercury a liquid even though its atoms are (obviously?) closely packed?
 
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  • #2
Water is anomalous in it's solid state being less dense than liquid.
It depends on the crystal structure which depends on the bond angle and chemical nature of the bonds.

Mercury is a liquid because it's outer electrons are very strongly bonded.
Strongly attatched outer electrons aren't free to bond with other atoms and so the metal is softer because it takes less energy to break the bonds. Mercury is the ultimate example of this.
Gold has a half full outer shell and so also has relatively weak bonds to other atoms and is a soft metal.
 
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  • #3
Ya, as was mentioned, water ice is an anomaly and the reason is because it forms a hexagonal lattice structure like the one shown here:

http://www.cs.cmu.edu/~dst/ATG/images/ice1h.gif

Therefore, if you look at the lattice structure you'll see that there is a lot of open space and thus it has a lower density. However, it is not the general case that a molecule will form such an open spacious lattice
 
  • #4
thanks mgb_phys and maverick_starstrider. i understand that water-ice is an anomaly.

Mercury is a liquid because it's outer electrons are very strongly bonded.
Strongly attatched outer electrons aren't free to bond with other atoms and so the metal is softer because it takes less energy to break the bonds. Mercury is the ultimate example of this.
Gold has a half full outer shell and so also has relatively weak bonds to other atoms and is a soft metal.

What are the outer electrons in mercury strongly bonded to? Do you mean that outer electrons(valence electrons right?) are not easily available to participate in reactions? In mercury, which is a metal, the outer electrons are 'free' in a sense to conduct electricity right?

Is that also why all the 'stable' elements like He, Ne, Ar etc are gases?
 
  • #5
The outer electrons - like all the others are strongly attracted to the nucleus, in mercury the large mass and charge of the nucleus mean the outer valence electrons are very strongly held - so aren't available to do the nomal free electron sea metal thing. (although they must have some freedom or mercury wouldn't be shiny!)

http://antoine.frostburg.edu/chem/senese/101/periodic/faq/why-is-mercury-liquid.shtml

The noble gases are gases because theie outer shells are completely full and so there are no free electrons to bond with other atoms of the same species. If the atoms are all on their own they are pretty much forced to be a gas. Interestingly mercury gas is single atoms like a noble gas.
 

1. Why is mercury a liquid at room temperature?

Mercury is a liquid at room temperature because its atoms are held together by weak metallic bonds. These bonds are not strong enough to keep the atoms in a fixed position, allowing them to move freely and causing the substance to take on a liquid form.

2. How do the closely packed atoms in mercury allow it to be a liquid?

The atoms in mercury are very closely packed, which means there is not much space between them. This allows for more movement and flexibility among the atoms, making it easier for them to slide past each other and take on a liquid form.

3. Why don't the closely packed atoms in mercury form a solid?

Even though the atoms in mercury are closely packed, they are not arranged in a rigid, organized structure like those in a solid. This lack of structure allows the atoms to move around more freely, preventing them from forming a solid state.

4. How does temperature affect the liquid state of mercury?

Temperature plays a major role in the liquid state of mercury. At room temperature, the weak metallic bonds between the atoms are not strong enough to keep them in a fixed position, resulting in a liquid form. However, at lower temperatures, these bonds become stronger, causing the substance to solidify into a metallic solid.

5. Can mercury ever become a solid?

Yes, mercury can become a solid at low temperatures. As mentioned earlier, the weak metallic bonds between the atoms become stronger at lower temperatures, causing the substance to solidify. This process is known as freezing or solidification.

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