1.6Unit 1. Structure, Bonding and Introduction to Organic Chemistry
Metallic bonding and structure — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions
5 min read 7 parts Lesson 8 of 36 Unit quiz
Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
Lesson summary
Metallic bonding and structure — IAL EDEXCEL LINEAR (CHEMISTRY) notes: Describe metallic bonding and use the lattice of positive ions and delocalised electrons to explain the melting point, conductivity, malleability and strength of metals and alloys.Metal atoms are tightly packe…
- Giant metallic lattice
- Metal atoms are tightly packed in a giant lattice, often in hexagonal layers or a cubic arrangement
- Outer-shell electrons are delocalised: free to move through the structure and not bound to one atom
- The atoms become positive metal ions held in a 'sea' of delocalised electrons
- The attraction keeps the lattice stable even though the positive ions repel one another
- Diagram: layers of positive ions surrounded by electrons, with both labelled (metal ions, delocalised electrons)
Part 1 of 5Metallic bonding and the lattice
Metal atoms are tightly packed in a giant lattice, often in hexagonal layers or a cubic arrangement.
Delocalised
Outer-shell electrons are delocalised: free to move through the structure and not bound to one atom.
The atoms become positive metal ions held in a 'sea' of delocalised electrons.
Metallic bond
Metallic bond electrostatic attraction between the positive ions and the delocalised electrons; it acts throughout the lattice and is non-directional.
The attraction keeps the lattice stable even though the positive ions repel one another.
Diagram: layers of positive ions surrounded by electrons, with both labelled (metal ions, delocalised electrons).
Part 2 of 5Strength of metallic bonding
Strength of metallic bonding
Metallic bonding is stronger with:
- more delocalised electrons per atom,
- a higher positive charge on the metal ions,
- smaller metal ions.
Example: melting point rises Na < Mg < Al.
Part 3 of 5Properties explained
| Property | Explanation |
|---|---|
| High melting and boiling points | Strong attraction between ions and the electron sea throughout a giant lattice; a lot of energy is needed to overcome it. Refer to metallic bonding, not separated molecules (metals are giant structures). |
| Conduct electricity | Delocalised electrons move through the lattice and carry charge when a potential difference is applied; the ions stay fixed and are not the charge carriers. |
| Conduct heat | Mobile electrons transfer kinetic energy rapidly through the lattice; vibrations of closely packed ions also transfer energy. |
| Malleable and ductile | Layers of ions slide over each other; the delocalised electrons move with the layers and keep attracting the ions, so the bonding is maintained and the crystal does not shatter (strong but flexible). |
Part 4 of 5Alloys
Alloys
An alloy forms when other atoms (e.g. carbon) are added to a metal lattice.
The different-sized atoms stop the layers of metal ions sliding easily, so alloys are stronger and harder than pure metals.
Part 5 of 5More from the specification
More from the specification
Electrolytic conduction in solution
- Electrolytic conduction in solution mobile hydrated cations and anions conduct electric charge when dissolved in an aqueous electrolyte solution.
Ionic bonds versus metallic electrostatic forces
- Ionic bonds versus metallic electrostatic forces electrostatic forces between ions create rigid ionic bonds, distinct from mobile sea electrons in metallic bonds.
Metallic bonding lattice model
- Metallic bonding consists of an electrostatic attraction between a regular lattice of positive metal cations and a delocalized 'sea' of mobile valence electrons.
Periodic trends in metallic bond strength
- Metallic melting points increase across a period as cationic charge increases and atomic radius decreases,
- (e.g. Na < Mg < Al)
- increasing delocalized electron density.
Electrical and thermal conductivity in metals
- Delocalized conduction electrons are free to move throughout the metallic lattice under an applied potential difference, conducting electric current and thermal energy.
Giant metallic lattice
- Giant metallic lattice regular lattice of positive metal ions surrounded by a sea of mobile delocalised valence electrons.
High melting points
- High melting points strong electrostatic attraction between positive ions and delocalised electrons requires substantial thermal energy to overcome.
Electrical conductivity of solid metals
- Electrical conductivity of solid metals applied potential differences cause delocalised electrons to drift freely through the rigid metallic lattice.
Ionic radius
- Distance from the nucleus to the outermost electrons of an ion.
Ionic compound
- A compound made of positive and negative ions held together by electrostatic attraction.
Ionic lattice
- A giant regular arrangement of alternating cations and anions.
Electrostatic force
- Force of attraction between opposite charges.
Atomic radius
- Half the distance between the nuclei of two bonded atoms of an element.
Electronic configuration
- The number of electrons in each shell, written with commas.
Ionic bond
- The strong electrostatic attraction between oppositely charged ions.
Period
- A row of the Periodic Table, equal to the number of occupied shells.
Compound
- Two or more elements chemically combined in a fixed ratio.
Anion
- A negative ion, formed when an atom gains electrons.
Proton
- Positive particle in the nucleus.
Non-metal
- An element that is usually a poor conductor and brittle when solid.
Density
- Mass divided by volume.
Key terms
| Term | Meaning |
|---|---|
| Delocalised electrons | Outer electrons free to move throughout a metal lattice. |
| Metallic bond | Electrostatic attraction between positive metal ions and delocalised electrons. |
| Giant metallic lattice | Regular arrangement of metal ions in a sea of electrons. |
| Malleable | Can be hammered into shape. |
| Ductile | Can be drawn into wire. |
| Alloy | Mixture of a metal with other atoms, stronger than the pure metal. |
Avoid these mistakes
1
Saying molecules or 'intermolecular forces' are overcome when a metal melts – metals are giant lattices; metallic bonds weaken.
2
Saying positive ions move and carry current in a solid metal – the delocalised electrons do.
3
Drawing the lattice without labelling the metal ions and the delocalised electrons.
4
Saying metal bonds break when the metal is hammered – the layers slide and the bonding is maintained.
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