✓ Revise Right course
When a molten binary ionic compound is electrolysed, the metal forms at the cathode and the non-metal forms at the anode. Free notes and 9 questions answered.
Products of Electrolysis in Molten Ionic Compounds is part of Electrolysis in GCSE AQA Higher Chemistry.
4 min
Reading time
24
Lessons in this topic
GCSE AQA Higher
Pathway
Reviewed by Revise Right
Content review
When a molten binary ionic compound is electrolysed, the metal forms at the cathode and the non-metal forms at the anode. Free notes and 9 questions answered.
AQA GCSE Chemistry mock draft, 26–31 Oct. Draft coverage: Chemistry Paper 1 (Higher tier). Reviewed for an original-practice sitting; check student availability before registering. Marking and results will follow later, after separate approval. Eligible new accounts receive a five-day Pro trial when signup email verification completes. Previous trials keep their original expiry. After expiry, new papers need Pro unless you have an explicitly confirmed free sitting offer for this event. That offer adds no Pro time or AI learning. Saved attempts and released results remain readable. No card or automatic charge.
Use this lesson to stay inside Electrolysis while connecting the detail back to the wider Topic 4: Chemical changes topic.
Read the core explanations from Products of Electrolysis in Molten Ionic Compounds before testing yourself from memory.
Picture heating table salt until it glows red-hot and becomes a liquid. Something remarkable happens - the solid crystals break apart and the ions become free to move. This molten salt can now conduct electricity, and when we pass current through it, we can split it back into its original elements.
This process - using electricity to break down compounds - is called electrolysis. When we electrolyse molten ionic compounds, we get pure elements at each electrode. No water, no complications, just the original metal and non-metal separated cleanly.
In molten lead bromide, we have lead ions (Pb²⁺) and bromide ions (Br⁻) moving freely. When we connect electrodes and switch on the power, these ions don't move randomly - they're attracted to opposite charges.
Think of it like magnets - opposites attract. The positive lead ions (Pb²⁺) are pulled towards the negative electrode (cathode). The negative bromide ions (Br⁻) are pulled towards the positive electrode (anode). This isn't random - it's the fundamental rule of electrolysis.
Here's where the key scientific idea happens. When ions reach the electrodes, they don't just sit there - they react. The electrodes force electrons onto some ions and pull electrons away from others. This transforms the ions back into neutral atoms.
At the cathode (negative electrode), metal ions gain electrons and become metal atoms. At the anode (positive electrode), non-metal ions lose electrons and become non-metal atoms or molecules. This is the universal pattern for molten ionic compounds.
Worked example: Electrolysis of Molten Lead Bromide
Predict the products when molten lead bromide (PbBr₂) is electrolysed using inert electrodes.
Answer: Lead metal forms at the cathode, bromine gas forms at the anode
Notice the pattern: metal at cathode, non-metal at anode. This happens because metals normally lose electrons, so at the cathode they are forced to gain electrons (reduction). Non-metals normally gain electrons, so at the anode they are forced to lose electrons (oxidation). The electrodes drive these reactions in the opposite direction to what happens spontaneously.
Every molten ionic compound follows the same rule. Take any binary ionic compound - one with just two elements - and you can predict exactly what forms where. The metal element appears at the cathode, the non-metal element appears at the anode.
This works for sodium chloride (Na at cathode, Cl₂ at anode), calcium oxide (Ca at cathode, O₂ at anode), or any other molten ionic compound. The key is remembering that molten means only the original ions are present - no water to complicate things.
The reason this pattern is so reliable comes down to electron movement. Cathodes pump electrons into the solution, anodes pull electrons out. Metal ions need electrons to become atoms, so they head to where electrons are being supplied. Non-metal ions need to lose electrons, so they head to where electrons are being removed.
Remember the phrase: AN OX, RED CAT. Anode = Oxidation (electron loss), Cathode = Reduction (electron gain). This applies to every electrolysis reaction, whether molten or aqueous.
Exam questions on this topic follow predictable patterns. You'll be given a molten ionic compound and asked to predict the products. The key is systematic thinking - identify the ions, work out where they go, then write what forms at each electrode.
The most common mistake is confusing molten electrolysis with aqueous electrolysis. In molten compounds, you only have the original ions present. In aqueous solutions, water molecules complicate things and can change the products completely.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-25.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Electrolysing molten lead bromide (PbBr₂) produces lead metal at the cathode and bromine gas at the anode. The electrode reactions are Pb²⁺ + 2e⁻ → Pb at the cathode and 2Br⁻ → Br₂ + 2e⁻ at the anode.
When a molten binary ionic compound is electrolysed, the metal forms at the cathode and the non-metal forms at the anode. For example, molten sodium chloride gives Na at the cathode and Cl₂ at the anode, and molten calcium oxide gives Ca and O₂.
Metals form at the cathode because the positive metal ions are attracted to the negative electrode, where electrons are supplied, and they gain electrons to become metal atoms. This gain of electrons is reduction.
Non-metals form at the anode because the negative non-metal ions are attracted to the positive electrode, where electrons are removed, and they lose electrons to form atoms or molecules. This loss of electrons is oxidation, for example 2Br⁻ → Br₂ + 2e⁻.
Molten electrolysis is more predictable because only the original ions are present, with no water to complicate things, so the products are always the original metal and non-metal. In aqueous solutions, water molecules can change the products completely.
Electrolysing molten calcium oxide produces calcium at the cathode and oxygen at the anode. Like every molten binary ionic compound, the metal forms at the cathode and the non-metal at the anode, because only the original ions are present.
A binary ionic compound is an ionic compound made of just two elements, such as lead bromide, sodium chloride or calcium oxide. When it is molten and electrolysed, the metal element appears at the cathode and the non-metal element at the anode.
Ion migration is the movement of ions towards electrodes of opposite charge during electrolysis. Positive ions, such as Pb²⁺, move to the negative electrode (cathode), and negative ions, such as Br⁻, move to the positive electrode (anode).
Lead ions gain electrons at the cathode to form lead metal: Pb²⁺ + 2e⁻ → Pb. In molten lead bromide, each Pb²⁺ ion gains 2 electrons, which is reduction, while bromide ions form bromine at the anode.