Structure and bonding · GCSE Chemistry
Metallic bonding
GCSE Chemistry revision on metallic bonding: positive ions in a sea of delocalised electrons, and why metals conduct, bend and often have high melting points.
Positive metal ions in a sea of delocalised electrons. Electrons move — that is conductivity. Layers of ions slide — that is malleability. Strong attraction — that is the high melting point of many metals.
The important bits
What you need to know
- 1
Metallic bonding is the electrostatic attraction between positive metal ions and a sea of delocalised electrons.
- 2
Metal atoms lose their outer electrons into a shared pool. Sodium contributes one electron per atom, magnesium two, aluminium three — which helps explain why Al has a higher melting point than Na.
- 3
Delocalised electrons can move through the structure, so metals conduct electricity as solids and as liquids, and they conduct heat well.
- 4
Layers of positive ions can slide over each other while the delocalised electrons hold the structure together, so metals are malleable and ductile.
- 5
Most metals have high melting and boiling points because the metallic attraction is strong and acts throughout the giant structure. Group 1 metals are softer and melt lower than transition metals.
- 6
Alloys are mixtures of metals (or a metal with carbon). Different-sized atoms distort the layers, so they cannot slide as easily — alloys are often harder than the pure metal.
- 7
Contrast with ionic crystals: when ionic layers slide, like charges line up and the crystal shatters. Metals do not shatter for that reason because the electron sea still binds the ions.
- 8
Graphite also conducts, but that is delocalised electrons in a giant covalent structure, not metallic bonding. Do not call graphite a metal.
Quotations worth analysing
Short evidence. Real method.
“Metals consist of positive ions surrounded by delocalised electrons.”
The ions are the metal atoms minus their outer electrons. The electrons are not attached to one atom. That pool is the reason metals conduct while solid.
“Cu²⁺(aq) + 2e⁻ → Cu(s)”
Copper metal formed at a cathode is the giant metallic structure again: positive ions plus the electrons that were gained. The half equation is reduction.
“Alloys are harder than pure metals because the layers cannot slide as easily.”
Different-sized atoms distort the regular layers. Steel (iron plus carbon) and bronze (copper plus tin) are standard examples. Pure copper is softer than brass.
Go deeper
Match the mobile charge carrier to the structure
Electrical conduction always needs charged particles that can move. In metals those particles are delocalised electrons, which is why a copper wire conducts while solid and while molten. In ionic compounds the particles are ions, free only when the lattice melts or dissolves. Simple molecules have neither, so they do not conduct. A common trap is “metals conduct because they have ions” without mentioning delocalised electrons, or “salt conducts because of electrons”. Write the carrier. Heat conduction in metals is the same electrons transferring energy. That is why a metal pan heats quickly and why graphite electrodes work: graphite has delocalised electrons too, but the bonding is covalent, not metallic.
Go deeper
Sliding layers explain shape; they do not explain melting
Malleable means you can hammer it into a sheet. Ductile means you can draw it into a wire. Both are sliding-ion stories with the electron sea still holding the metal together. Melting is different: you must give the ions enough energy to leave their regular packing, which needs a lot of energy in a metal with strong metallic bonds. Sodium melts at 98 °C; iron at 1538 °C. More delocalised electrons and a stronger attraction to the positive ions make the bond stronger. Do not use “layers slide” to explain a high melting point — that explanation is for why the solid can change shape without breaking.
Go deeper
Alloys are a particle-size argument
In pure iron the atoms are the same size and layers slide. Add carbon (steel) or chromium and nickel (stainless steel) and the regular packing is disrupted. The metal is harder and less malleable. That is a six-mark materials question sitting inside Chemistry. You do not need the full metallurgy: different-sized atoms, distorted layers, harder to slide. Link it back to metallic bonding so the examiner sees you still know the structure is positive ions plus delocalised electrons, just no longer in a perfectly regular stack. Brass (copper and zinc) is the same argument with a named alloy.
See the idea in action
Explain why copper conducts electricity and can be drawn into wires, but solid ionic copper chloride does not conduct and is brittle. Copper is a giant metallic structure: delocalised electrons move and carry charge, and layers of Cu²⁺ ions can slide while the electron sea holds the metal together (ductile). Copper chloride is a giant ionic lattice. In the solid the ions cannot move, so it does not conduct. If you hit it, layers shift, like charges align, and the crystal shatters.
Exam technique
Turn knowledge into marks
For metals, write positive ions, delocalised electrons, then the property. Conductivity = electrons move. Malleability = layers slide. Melting point = strong attraction throughout the giant structure. Mention alloys when asked about hardness.
Common mistakes
Do not give these marks away
- 01
Saying metals are ionic, or that they conduct because ions move through the solid metal.
- 02
Using “layers slide” to explain high melting point instead of malleability.
- 03
Claiming graphite is metallic, or that pure metals are always harder than alloys.
Why are metals malleable?
AIonic bonds break and reform
BLayers of positive ions can slide while delocalised electrons hold the metal together
CMetal atoms are covalently bonded in simple molecules
DMetals contain weak intermolecular forces
Show the answer
Layers of positive ions can slide while delocalised electrons hold the metal together. The electron sea still attracts the ions after the layers move, so the metal changes shape instead of shattering like an ionic crystal.
Quick questions
If this is the bit you searched
What is metallic bonding GCSE Chemistry?
The electrostatic attraction between positive metal ions and a sea of delocalised electrons in a giant structure.
Why do metals conduct electricity?
Delocalised electrons can move through the metallic structure and carry charge, including when the metal is solid.
Why are alloys harder than pure metals?
Atoms of different sizes distort the layers of ions, so the layers cannot slide over each other as easily.
How is metallic bonding different from ionic bonding?
Metals have delocalised electrons and sliding layers of ions, so they conduct as solids and are malleable. Ionic lattices conduct only when ions can move (molten or aqueous) and are brittle.