Molecular compounds do not conduct electricity because they lack mobile ions. In order for a substance to conduct electricity, it must contain free-moving charged particles, such as ions or electrons.

In molecular compounds, the atoms are held together by covalent bonds, which are non-polar and do not produce ions. As a result, there are no free charges in a molecular compound that can move and carry an electric current. In contrast, ionic compounds, which are composed of positively and negatively charged ions, readily conduct electricity because the ions can move freely and carry the current.