Why does salts conduct electricity?

Answer 1

Basic Facts First:

1. Pure dry salt does not conduct electricity.
2. Salt dissolved in water does conduct electricity.
3. If pure salt is heated to nearly a thousand degree Celsius, it becomes molten salt and does conduct electricity.

This is true for any salt, whether highly soluble (sodium chloride, silver nitrate,
magnesium sulfate, lithium bromide, cesium chloride) or almost insoluble (silver chloride, barium sulfate, antimony sulfide, cadmium sulfide, calcium carbonate). Salts don't conduct in solid dry form, but do in water. If even a little bit dissolves in water then the solution is a little conducting and becomes more conducting as more is dissolved. When a salt is heated to a molten liquid, whether at a few hundred degrees or a thousand degrees, the molten salt will conduct electricity quite well.

Basic Explanation:

The basic explanation for table salt and all other salts is the same and the explanation as to why can be stated simply as "fee charges."

Pure solid Salt is a crystal with positive and negative ions arranged in almost perfectly regular rows. Everybody is charged, but nobody can move so applying a voltage does not dislodge atoms from the crystal lattice sites. The atoms have electrons, but they too are tightly bound to the parent ion and won't move under any realistic voltage. There is a lot of charge, but it is not free to move, hence nonconducting.

Salt Solutions are a collection of charged ions moving more or less freely through water. If a voltage is applied, the ions move (positive one way and negative the opposite) because they feel force caused by the electric field the voltage creates. Electrons are still pretty much stuck to the ions, so the current is the moving charged ions. Salt solutions have charged atoms free to move, so they conduct electricity.

Molten Salt has the same ions as the solid crystalline salt, but they are no longer confined to a crystal structure. The positive and negative ions are free to move in the molten liquid and there is no water around, so the molten form of salt has a lot of ions and they are free to move, so molten salts conduct electricity well.

Some Specific Details:
Table salt in the normal dry form of salt crystals has a very low electrical conductivity and is classified as an insulator. All solid salts have this property. Depending on the purity and extent to which water may be present, it would normally be found that salt has a resistivity in excess of a million ohm-meters.

Typical metals have less than one millionth of an ohm-meter.

For comparison, good insulators such as glass or rubber have resistivities

of more than a billion ohm-meters.

If table salt is mixed with water, then it dissolves and sodium and chlorine ions go into solution and salt water has good conductivity. Seawater, for instance has about 0

.2 ohm-meters

resistivity which is a lot less than a metal but a lot more than dry table salt.

Table salt can also be heated to a temperature where it melts (801 centigrade). When any type of salt melts, it becomes a collection of molten charged atoms and conducts electricity well, though not as well as a metal.

Answer 2

it only conducts electricity when in a solution. salts have ions in them (which carry electric charge) and when salt is put into solution then the ions are free to move about and conduct the electric charge