Electrolysis of molten binary ionic compounds

A binary ionic compound contains ions of two elements: a metal and a non-metal. When the compound is melted, its ions are free to move. The molten liquid can therefore conduct electricity and be broken down into its elements by electrolysis.

Two inert electrodes are placed in the molten compound and connected to a power supply. Inert electrodes do not react, so the products come from the ions in the molten compound.

Positive metal ions move to the cathode, the negative electrode. They gain electrons and are reduced, forming the metal element.
Negative non-metal ions move to the anode, the positive electrode. They lose electrons and are oxidised, forming the non-metal element.

An ion is discharged when it gains or loses electrons at an electrode and becomes part of a neutral product. To predict the products of a molten binary ionic compound, identify its metal cation and non-metal anion: the metal forms at the cathode and the non-metal forms at the anode.

Electrolysis of molten lead(II) bromide

Molten lead(II) bromide, $\ce{PbBr2}$ , contains lead ions, $\ce{Pb^{2+}}$ , and bromide ions, $\ce{Br^-}$ .

At the cathode, each lead ion gains two electrons. Lead metal is produced:

\ce{Pb^{2+} + 2e^- -> Pb}

At the anode, bromide ions lose electrons and form bromine molecules. Two bromide ions each lose one electron to produce one molecule of bromine:

\ce{2Br^- -> Br2 + 2e^-}