AQA GCSE Combined Science Foundation (8464), Foundation tier · Chemistry › Bonding, structure, and the properties of matter › Chemical bonds, ionic, covalent and metallic
Practise Metallic bonding. 6 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How the atoms in a metal are held together: a giant structure of positive ions in a regular pattern, with delocalised electrons that are free to move through it. It is usually tested with 2 to 3 mark 'describe' questions or diagram labelling, and it is the key to explaining the properties of metals.
Key facts
Metal = giant structure of atoms in a regular pattern (layers)
Outer shell electrons are delocalised: free to move through the whole structure
Metallic bond = strong electrostatic attraction between positive ions and delocalised electrons
Charge on each ion = number of outer electrons given up (Na+, Mg2+)
Alloys have metallic bonding too
Strong bonds → high melting points; delocalised electrons → conduction
Notes
The structure of a metal
Metals have giant structures of atoms arranged in a regular pattern, in layers.
The electrons in the outer shell of each metal atom are delocalised: they do not belong to any one atom and are free to move through the whole structure.
Once an atom has lost its outer electrons in this way, it is a positive ion. So a metal can be described as positive ions surrounded by delocalised electrons.
The metallic bond
The delocalised electrons are shared by all the ions. This sharing gives strong metallic bonds.
The bond is the strong electrostatic attraction between the positive metal ions and the negative delocalised electrons.
The attraction acts throughout the giant structure, so there are a very large number of strong bonds.
Alloys have metallic bonding too: they are mixtures of a metal with other elements, with delocalised electrons throughout.
Drawing metallic bonding
diagram
Draw regular rows of circles, each marked + (or with the ion's charge, e.g. 2+ for magnesium).
Draw electrons (e− or small dots) scattered between the ions and label them 'delocalised electrons'.
Metallic bonding: attraction between positive ions and delocalised electrons.
Like any model, this shows only a tiny part of the structure and is not to scale.
Why metallic bonding matters
Metallic bonding explains the properties of metals: strong bonds give high melting points, layers of ions allow metals to be bent and shaped, and delocalised electrons that can move make metals conduct electricity and thermal energy.
You use these ideas in 'Properties of metals and alloys' and 'Metals as conductors'.
How to answer each type of question
Label a diagram of metallic bonding
2 marksGrade 4
The particles in regular rows marked + are positive (metal) ions.
The small particles spread between them are delocalised electrons.
Example. The diagram shows the structure of a metal.
(a) Name the particles marked +. (b) Name the particles marked e−.
Say it is a giant structure of atoms (positive ions) in a regular pattern, in layers.
Say the outer electrons are delocalised and free to move through the structure.
Say there is strong electrostatic attraction between the positive ions and the delocalised electrons.
Example. Describe the structure and bonding in copper.
Show the model answerHide the model answer
A giant structure of copper atoms (positive ions) arranged in a regular pattern / in layers (1). The outer shell electrons are delocalised, so they can move through the whole structure (1). There is strong electrostatic attraction between the positive ions and the delocalised electrons (1).
Don’t lose marks
Saying the positive ions move. It is the delocalised electrons that move; the ions stay in their positions.
Writing 'free electrons' or 'a sea of electrons' without the word 'delocalised'. Use 'delocalised' to be safe.
Describing the bond as attraction between atoms, or between electrons. It is between positive ions and delocalised electrons.
Calling metallic bonding ionic because the diagram shows ions. There are no negative ions in a metal.
More tips
Memory tricks
Picture rows of positive ions held together by a cloud of moving electrons. The 'glue' is the attraction between + and −.
Labelling check: the + particles are ions (not atoms or protons); the moving particles are electrons (not ions).
One structure explains every metal property: strong bonds → high melting point; layers → can be bent; delocalised electrons → conducts.
Exam technique
In 'describe the bonding' questions, three things score: a giant regular structure, delocalised electrons, and attraction between positive ions and delocalised electrons.
If you draw a diagram, label both the positive ions and the delocalised electrons.
Call metallic bonds 'strong': you need this word later to explain high melting points.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State that metals have giant structuresThe atoms in a metal are arranged in a regular pattern in a giant structure.
Grade 4
Describe what delocalised electrons areThe outer shell electrons of metal atoms are delocalised: free to move through the whole structure.
Grade 5
Describe the metallic bondStrong electrostatic attraction between positive metal ions and the shared delocalised electrons.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Metals have metallic bonding. What are delocalised electrons?
Electrons that are free to move through the whole structure.
The electronic structure of magnesium is 2,8,2. In magnesium metal, the outer electrons of each atom are delocalised. What is the charge on the positive ions in magnesium metal?
2+
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Metals have metallic bonding.
(a) Complete the sentence. Tick (✓) one box. Metals consist of giant structures of atoms arranged in a ................[1]
random pattern
regular pattern
single layer
small molecule
(b) What are delocalised electrons?[1]
(c) Which electrons become delocalised in a metal? Tick (✓) one box.[1]
All of the electrons
Electrons in the inner shells
Electrons in the outer shell
One electron from every ten atoms
(d) Are metallic bonds strong or weak?[1]
Show the answer and mark scheme
(a)Answer: regular pattern
(b)Answer: Electrons that are free to move through the whole structure.
electrons that are free to move (through the whole structure)
(c)Answer: Electrons in the outer shell
(d)Answer: strong
strong
Question 2Medium5 marks
The electronic structure of magnesium is 2,8,2. In magnesium metal, the outer electrons of each atom are delocalised.
(a) What is the charge on the positive ions in magnesium metal?[1]
(b) How many delocalised electrons are there in a piece of magnesium that contains 5000 atoms?[1]
(c) The positive ions in a metal repel each other. Explain why the structure does not fall apart.[2]
(d) Magnalium is an alloy of magnesium and aluminium. What type of bonding is present in magnalium?[1]
Show the answer and mark scheme
(a)Answer: 2+
2+
(b)Answer: 10 000
10 000
(c)Answer: The delocalised electrons are attracted to all the positive ions; this strong electrostatic attraction holds the ions together.
the (negative) delocalised electrons attract the positive ions
this (strong) electrostatic attraction holds the structure together / is stronger than the repulsion