Why is ionic solid non-conductive, yet its solutions in water, or in the liquid state, it carries a charge?

3 Answers
Sep 13, 2015

Simple, binary ionic solids are composed of a positive ion and and a negative ion. In the solid state they are not free to move. In the liquid or molten state, they are free to move, and can therefore carry a current.


Take a simple salt such as #NaCl#. We might represent this as #Na^+Cl^-#. Now in the solid state, each cation (#Na^+#) is directly bound to 6 anions (#Cl^-#), and vice versa. There are secondary interactions throughout the lattice, and the solid state structure is highly ordered and stable. The individual ions are not free to move, and are held in an electrostatic lattice in fixed positions.

If the lattice is disrupted, say by supplying (a lot of!) heat to give molten #NaCl#, or more simply by dissolving the ionic solid in water, the individual ions are free to move, and can therefore transfer a current. Note that not all ionic solids are soluble in water; it depends on the strength of the lattice.

Sep 13, 2015

This is due to the arrangement of ions...


In the solid state, the ions are held in fixed positions in a crystal lattice held together by strong electrostatic forces of attraction. Thus, there's no mobile charge carriers to conduct electricity.

In the molten state, the ions are free to move around to conduct electricity.

Apr 15, 2016

Ions are charged particles and donot conduct electricity when in solid state because the ions are not free to move.However when in molten or dissolved the ions are then free to move and they conduct electricity.