What is metallic bonding and how does it occur?

Metallic bonding is a type of chemical bonding that occurs between atoms of metallic elements. It involves the sharing of free electrons among a lattice of metal atoms. These electrons are delocalized, meaning they are not bound to any specific atom, allowing them to move freely throughout the metal structure. This electron sea model explains many properties of metals, such as conductivity and malleability.

How does metallic bonding contribute to the properties of metals?

Metallic bonding contributes to several characteristic properties of metals. The delocalized electrons allow metals to conduct electricity and heat efficiently. The strong attraction between the positive metal ions and the electron cloud gives metals their strength and high melting and boiling points. Additionally, the ability of the electrons to move freely allows metals to be malleable and ductile, meaning they can be shaped and stretched without breaking.

Why are metals good conductors of electricity?

Metals are good conductors of electricity due to the presence of delocalized electrons in metallic bonding. These electrons can move freely throughout the metal lattice, allowing them to carry an electric charge across the metal. This free movement of electrons is what enables metals to conduct electricity efficiently.

What is the difference between metallic bonding and ionic bonding?

The main difference between metallic bonding and ionic bonding lies in the nature of the bond and the types of elements involved. Metallic bonding occurs between metal atoms and involves a 'sea' of delocalized electrons. In contrast, ionic bonding occurs between metals and non-metals and involves the transfer of electrons from one atom to another, resulting in the formation of positively and negatively charged ions. This difference in bonding leads to distinct properties in metals and ionic compounds.

How does the structure of metallic bonds affect the melting and boiling points of metals?

The structure of metallic bonds, characterized by a lattice of positive metal ions surrounded by a sea of delocalized electrons, contributes to the high melting and boiling points of metals. The strong electrostatic attraction between the ions and the electron cloud requires a significant amount of energy to overcome, resulting in high melting and boiling points. This makes metals generally solid at room temperature, with exceptions like mercury.

Why is "Saying electrons are 'shared' in metallic bonding" a common mistake in Metallic Bonding?

Why it happens: Confusing with covalent. How to avoid it: Use 'DELOCALISED' (not shared, not transferred). Source: 0620/42 — recurring

Why is "Saying metals are malleable because the bonds break easily" a common mistake in Metallic Bonding?

Why it happens: Misunderstanding the model. How to avoid it: Bonds DON'T break — layers slide while still being held by delocalised electrons.

Why is "Drawing metal atoms (rather than ions) in the lattice" a common mistake in Metallic Bonding?

Why it happens: Forgetting electrons are removed. How to avoid it: Atoms have lost outer electrons → drawn as POSITIVE IONS (e.g. Na^+, Mg^2+).

Atoms, Elements and CompoundsCambridge IGCSE Chemistry 0620 Extended

Metallic Bonding

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Metallic Bonding — Cambridge IGCSE 0620 Chemistry Extended (2026)

Positive metal ions in a sea of delocalised electrons. Why metals conduct, can be hammered into shape, and have high m.p.

What you’ll learn

Mapped to the Cambridge IGCSE 0620 syllabus (2026-2028).

2.4 — Describe the lattice of positive ions in a sea of electrons.
2.4 — Explain physical properties of metals using metallic bonding.

The metallic bond

Metal atoms donate outer electrons to a delocalised sea; positive ions sit in the lattice.

Setup. In a metal:

Each atom donates its outer-shell electrons to a 'sea' shared by all the metal ions.
The metal atoms become positive ions (cations), arranged in a regular lattice.
The delocalised electrons can move freely throughout the metal.
The bonding is the strong electrostatic attraction between the positive ions and the negative sea.

Two parts to remember:

Lattice of positive ions (where atoms once were).
Sea of delocalised electrons (the donated outer electrons, free to roam).

This bonding is in 3D. Layers of ions stacked together, with electrons moving in the spaces between.

Cambridge tip. When asked to "describe the bonding in a metal", say BOTH:

Lattice of positive ions.
Surrounded by a sea of delocalised electrons.
Strong electrostatic attraction between them.

Regular lattice of positive metal ions held together by a shared sea of delocalised electrons.

Positive metal ions in a regular lattice.
Sea of delocalised electrons.
Electrostatic attraction holds them together.
Strong, in 3D.

Properties explained

Conducts (delocalised e⁻), malleable (layers slide), high m.p. (strong attraction).

1. Electrical conductivity. Delocalised electrons can move through the lattice and carry charge. Metals conduct as solids AND in molten form (no need to melt them, unlike ionic compounds).

2. Thermal conductivity. Delocalised electrons also transfer kinetic energy quickly through the metal. That's why metals feel cold when you touch them — they conduct heat away from your skin.

3. Malleability and ductility.

Malleable: can be hammered into thin sheets.
Ductile: can be drawn into wires.

When force is applied, the layers of metal ions slide over each other. The delocalised electrons follow along — the metallic bonding is preserved. The metal deforms WITHOUT shattering. Compare with ionic compounds, which crack along cleavage planes when ions are displaced.

Layers of ions slide over one another; the electron sea keeps the bonding intact, so the metal bends instead of breaking.

4. High melting and boiling points. Strong electrostatic attraction across the entire lattice → lots of energy needed to break it. Most metals melt at $> 600\degree\text{C}$ .

Notable exception: mercury (m.p. $-39\degree\text{C}$ ) — only liquid metal at room temp.

5. Shiny appearance. Delocalised electrons absorb and re-emit photons of all visible wavelengths → silvery reflective lustre.

6. High density. Atoms tightly packed in the lattice.

Worked qualitative. Why is copper a good electrical wire material? It has many delocalised electrons (high conductivity), is ductile (can be drawn into wires), is malleable (easily worked), and is reasonably cheap. It also forms an oxide layer (verdigris) that protects underlying copper from further corrosion.

Worked qualitative. Why does an iron rod feel cold when you touch it but a wooden stick at the same temperature feels warm? Iron's delocalised electrons quickly conduct heat AWAY from your fingers. Wood is a poor conductor; little heat flows.

Conducts (electrons & heat).
Malleable & ductile (layers slide).
High m.p. (strong attraction).
Shiny, dense.

Alloys (extension)

A mixture of a metal with another element. Often harder than the pure metal because layers can't slide as easily.

Alloy. A mixture of a metal with one or more other elements (often another metal).

Why alloy? Pure metals are often too soft for engineering uses. Alloying makes them harder by DISRUPTING the regular layer arrangement: when atoms of different sizes are mixed in, the layers can't slide as easily.

Common alloys.

Brass = copper + zinc. Used for instruments, fittings.
Bronze = copper + tin. Used for statues, bearings.
Steel = iron + carbon (and trace others). Stronger than iron.
Stainless steel = iron + chromium + nickel. Resistant to corrosion.

Worked qualitative. Why is steel harder than pure iron? Carbon atoms are smaller than iron atoms; they fit in the gaps in the iron lattice and prevent layers from sliding past each other.

Cambridge tip. When asked "explain why an alloy is harder than the pure metal", mention DIFFERENT-SIZED atoms disrupting layer sliding.

Alloy: metal + other element(s).
Harder than pure metal.
Different atom sizes block layer sliding.
Examples: brass, bronze, steel.

How it’s examined

Metallic bonding appears every Paper 2 (3-4 marks: describe the bond, properties) and Paper 4 (4-6 marks: explain a property, alloy hardness). Examiner reports flag students saying 'metallic bond is between metals and non-metals' (that's IONIC bonding).

Sources: Cambridge IGCSE Chemistry 0620 syllabus 2026-2028 (2.4); 0620/22 May/Jun 2024 — Q6 (metallic bonding, alloys); 0620 Examiner Reports 2022-2024. Last reviewed 2026-05-06.

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Step-by-step worked examples — Metallic Bonding

Step-by-step solutions to past-paper-style questions on metallic bonding, written exactly the way a tutor would explain them at the board.

1Describe the metallic-bonding model
Extended• model
Question
Describe metallic bonding.
Step-by-step solution
1. Step 1
  Lattice of positively-charged metal ions surrounded by a 'sea' of delocalised outer-shell electrons.
2. Step 2
  Strong electrostatic attraction between the positive ions and the delocalised electrons.
Answer
Positive metal ions in a sea of delocalised electrons; electrostatic attraction holds the lattice together.
2Why metals conduct electricity
Extended• Adapted from 0620/42 May/Jun 2024 Q7• conductivity
Question
Explain why metals conduct electricity.
Step-by-step solution
1. Step 1
  Delocalised electrons are FREE to move through the lattice.
2. Step 2
  When a pd is applied, these electrons drift → current flows.
Answer
Free, delocalised electrons can carry charge through the lattice.
3Why metals are malleable
Extended• malleability
Question
Explain why metals can be hammered into shape (malleability).
Step-by-step solution
1. Step 1
  Layers of metal ions can SLIDE over each other because the electron sea is non-directional.
2. Step 2
  After sliding, the bonding is unchanged (still ions + sea of electrons).
Answer
Layers of ions slide; the delocalised electrons keep them bonded after sliding.
4Why most metals have high melting points
Extended• properties
Question
Explain why iron has a much higher melting point than sodium.
Step-by-step solution
1. Step 1
  Both have metallic bonding. Iron contributes more delocalised electrons per atom and forms a higher charge ion.
2. Step 2
  Stronger electrostatic attraction → more energy needed to melt.
Answer
More delocalised electrons / higher ionic charge → stronger metallic bonding → higher m.p.

Key Definitions and Keywords — Metallic Bonding

Definitions to memorise and the exact keywords mark schemes credit for metallic bonding answers — sharpened from recent examiner reports for the 2026 0620 sitting.

Metallic bond
Examiner keyword
Electrostatic attraction between a lattice of positive metal ions and the surrounding sea of delocalised outer-shell electrons.
Delocalised electrons
Examiner keyword
Outer-shell electrons that are not bound to a specific atom and are free to move through the metal lattice.
Malleable
Examiner keyword
Can be hammered or rolled into thin sheets without breaking.
Ductile
Examiner keyword
Can be drawn into wires.

Common Mistakes and Misconceptions — Metallic Bonding

The traps other students keep falling into on metallic bonding questions — taken from recent Cambridge IGCSE 0620 examiner reports and mark schemes — and how to avoid them.

✕Saying electrons are 'shared' in metallic bonding
0620/42 — recurring
Why it happens
Confusing with covalent.
How to avoid it
Use 'DELOCALISED' (not shared, not transferred).
✕Saying metals are malleable because the bonds break easily
Why it happens
Misunderstanding the model.
How to avoid it
Bonds DON'T break — layers slide while still being held by delocalised electrons.
✕Drawing metal atoms (rather than ions) in the lattice
Why it happens
Forgetting electrons are removed.
How to avoid it
Atoms have lost outer electrons → drawn as POSITIVE IONS (e.g. $\text{Na}^{+}$ , $\text{Mg}^{2+}$ ).

Practice questions

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Metallic Bonding — frequently asked questions

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Metallic Bonding

Short Study Notes in the form of Slides

Short Study Notes — Metallic Bonding

Detailed Notes

What you’ll learn

How it’s examined

1Describe the metallic-bonding model

2Why metals conduct electricity

3Why metals are malleable

4Why most metals have high melting points

Metallic bond

Delocalised electrons

Malleable

Ductile

✕Saying electrons are 'shared' in metallic bonding

✕Saying metals are malleable because the bonds break easily

✕Drawing metal atoms (rather than ions) in the lattice

Practice questions

Past paper style quiz

Assess your understanding

Video lesson

Metallic Bonding — frequently asked questions