Hi
these are the posts from earlier---i just had a quetsion about your response:
""Apchemistry - DrBob222, Monday, April 26, 2010 at 7:10pm
Your thinking is ok. All ionic solids, although composed of ions, are locked into place by the crystal lattice structure of the compound. Thus the ions are not free to move about and they can not conduct electricity. """
*****my question is: even though the ions are not free to move about, don't they still have vibrational energy, if not translational and rotational? Doesn't the answer have to be related to electrons' movement? (i was thinking, in metallic solids, there is a sea of electrons, but in ionic solids, there is no such "sea" (?because the electrons are involved in the lattice structure of the ionic solid) so the electrons cannot freely flow so current cannot flow??
does this sound correct?
Thank you!!!!!
I am a little confused; I think you may have contradicted yourself. I'll try to answer each part of your response.
Yes, the ions in a crystal lattice do posses some vibrational energy and I suppose it would not be outlandish to suggest that one or two of them (out of billions and billions and billions) might even have rotational and/or translational energy (IF they could break loose from the lattice). You are also correct that there is no sea of electrons as in a metallic conductor. The electrons; however, ARE moving (and moving very very fast). The ion itself is not moving from point to point but the electrons are moving in their respective shells and orbitals. Here is an example which I'm sure you have read about. An ionic crystal, such as NaCl, will not conduct electricity in the solid state precisely because the ions can't move and transport the electrical charge from one electrode to the other. BUT, what happens if we melt the NaCl, thus breaking the crystal lattice structure? I"m thinking the melting point of NaCl is about 800 C or so BUT in the molten state, the crystal lattice is broken, the ions are free to move more or less freely within the liquid, and it DOES conduct electricity, precisely because the ions CAN move from point A to point B.
Yes, you are correct in your thinking. In ionic solids, the ions are indeed not free to move about and conduct electricity. However, they do possess vibrational energy due to their vibrational motion within the crystal lattice structure. This vibrational energy is not sufficient to allow the ions to move freely and carry an electric current.
The reason why the ions are not free to move and conduct electricity in ionic solids is indeed related to the movement of electrons. In metallic solids, there is a "sea" of delocalized electrons that are not bound to any particular atom but can move freely throughout the solid. This movement of electrons allows for the flow of electric current in metallic solids.
In contrast, in ionic solids, the electrons are involved in the lattice structure, meaning they are tightly bound to their respective ions and are not free to move. The strong electrostatic forces between the positively and negatively charged ions prevent the ions from moving and conducting electricity.
So, in summary, your explanation is correct. The lack of free-moving electrons in ionic solids prevents the flow of electric current, while in metallic solids, the presence of a "sea" of delocalized electrons allows for the flow of electric current.