Metallic Bonding
Section: 2. Atoms, Elements & Compounds | Syllabus: Cambridge AS Level Physics 9702
What is Metallic Bonding? Metallic Bonding The strong electrostatic attraction between positive metal ions (cations) and the 'sea' of delocalized electrons that are free to move throughout the metal structure.
Metallic bonding is the type of chemical bonding that occurs in metals and metal alloys. It gives metals their characteristic properties. Occurs in metallic elements and alloys Involves metal atoms losing outer electrons Creates positive metal ions (cations) Released electrons become delocalized (free to move) Results in a giant metallic structure Key Concept In metallic bonding, electrons are not bound to any particular atom - they are delocalized and free to move throughout the entire metal structure.
This is fundamentally different from ionic and covalent bonding. How Metallic Bonding Forms Step-by-Step Process Metal atoms lose outer electrons: Each metal atom releases one or more electrons from its outer shell Positive ions form: The atoms become positive ions (cations) because they've lost negative electrons Electrons become delocalized: The released electrons are no longer attached to any particular atom - they can move freely Regular lattice forms: The positive ions arrange themselves in a regular pattern Electrostatic attraction: The positive ions are attracted to the 'sea' of negative delocalized electrons Metal atom → Metal ion⁺ + electron⁻ Example: Na → Na⁺ + e⁻ Example: Mg → Mg²⁺ + 2e⁻ Important The delocalized electrons don't belong to any specific atom - they're shared by all the metal ions in the structure.
This is why we call it a "sea of electrons." Structure of Metals Giant Metallic Structure Metals have a giant metallic lattice structure : Positive metal ions arranged in a regular 3D pattern Delocalized electrons (electron 'sea') moving freely throughout the structure Strong electrostatic forces between positive ions and negative electrons in all directions Giant structure: Millions of atoms bonded together Non-directional bonding: Forces act equally in all directions Visualizing the Structure Imagine the positive metal ions as a rigid framework of balls, with the delocalized electrons as a mobile 'sea' flowing between and around them.
The electrons hold the structure together like glue. Properties of Metals Property 1: Good Electrical Conductivity Observation Metals conduct electricity in solid and liquid states Explanation: Metals contain delocalized electrons that are free to move When a voltage is applied, electrons can flow through the metal Moving electrons carry electric charge from one end to the other This works in both solid and molten states Unlike ionic compounds, metals conduct when solid because electrons (not ions) carry the charge Material Type Conducts as Solid?
Why? Metals ✓ Yes Delocalized electrons free to move Ionic compounds ❌ No Ions fixed in lattice (conduct when molten) Simple molecular ❌ No No charged particles Giant covalent ❌ No (except graphite) No free electrons Property 2: Good Thermal Conductivity (Heat) Observation Metals conduct heat very well Explanation: Delocalized electrons can transfer kinetic energy quickly throughout the metal When one part is heated, electrons gain energy and move faster These high-energy electrons collide with other electrons and ions Energy spreads rapidly through the structure This is why metal spoons get hot quickly and metal pans heat evenly Property 3: Malleability Malleable Can be hammered or rolled into different shapes without breaking.
Explanation: When force is applied, layers of metal ions can slide over each other The metallic bonding is non-directional - it acts equally in all directions As layers slide, the delocalized electrons move with them The bonding remains strong even after deformation The metal doesn't shatter like ionic compounds do Contrast with Ionic Compounds Ionic compounds are brittle - when layers slide, like charges repel and the crystal shatters.
Metals are malleable - when layers slide, the electron sea maintains bonding and the metal just changes shape. Property 4: Ductility Ductile Can be drawn out into wires without breaking. Explanation: Similar reason to malleability Layers can slide past each other when pulled Metallic bonding remains intact as the metal is stretched Delocalized electrons continue to hold the structure together Property 5: High Melting and Boiling Points Observation Most metals have high melting points (though there's variation) Explanation: Metals have giant structures with strong metallic bonding throughout Strong electrostatic forces between positive ions and delocalized electrons A lot of energy needed to overcome these forces and separate the ions Breaking metallic bonds requires high temperatures Metal Melting Point (°C) Explanation Tungsten (W) 3422 Very strong metallic bonding Iron (Fe) 1538 Strong metallic bonding Copper (Cu) 1085 Strong metallic bonding Sodium (Na) 98 Weaker metallic bonding (1 electron) Mercury (Hg) -39 Weak metallic bonding (liquid at roo…
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