* GCSE Chemistry & AS Revision Notes Chemical Bonding Part 5 METALLIC BONDING properties of metals *

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 Doc Brown's Chemistry - Chemical Bonding - Revision Notes

 Part 5 Metallic Bonding, Structure and Properties 

Revision KS4 Science IGCSE/O level/GCSE Chemistry Information Study Notes for revising for AQA GCSE Science, Edexcel 360Science/IGCSE Chemistry & OCR 21stC Science, OCR Gateway Science  (revise courses equal to US grades 9-10) Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA OCR Edexcel Salters CIE revising courses for pre-university students (equal to US grade 11 and grade 12 and Honours/honors level courses)

Part 1 Introduction - why do atoms bond together? & sub-index for Parts 2-5 (read 1st)

Part 2 Ionic Bonding - compounds and properties

Part 3 Covalent Bonding -small simple molecules and properties

Part 4 Covalent Bonding - macromolecules and giant covalent structures

Part 5 Metallic Bonding - structure and properties of metals (this page)

Part 6 More advanced concepts for advanced level chemistry (in preparation, BUT a lot on intermolecular forces in Equilibria Part 8)



Part 5.  METALLIC BONDING - structure and properties of metals

metal bonding model element/alloys * physical properties of metals


(c) doc b BONDING IN METALS

  • (c) doc bA giant metallic lattice. The crystal lattice of metals consists of ions NOT atoms surrounded by a 'sea of electrons' forming another type of giant lattice.
  • The outer electrons (-) from the original metal atoms are free to move around between the positive metal ions formed (+).
  • These free or 'delocalised' electrons are the 'electronic glue' holding the particles together.
  • There is a strong electrical force of attraction between these mobile electrons (-) and the 'immobile' positive metal ions (+) and this is the metallic bond.
  • Metallic bonding is not directional like covalent bonding, it is like ionic bonding in the sense that the force of attraction between the positive metal ions and the mobile electrons acts in every direction about the fixed (immobile) metal ions.

 Explaining the physical properties of metals

  • This strong bonding generally results in dense, strong materials with high melting and boiling points.

    • Usually a relatively large amount of energy is needed to melt or boil metals. Energy changes for the physical changes of state of melting and boiling for a range of differently bonded substances are compared in a section of the Energetics Notes.

  • Metals are good conductors of electricity because these 'free' electrons carry the charge of an electric current when a potential difference (voltage!) is applied across a piece of metal.

  • Metals are also good conductors of heat. This is also due to the free moving electrons. Non-metallic solids conduct heat energy by hotter more strongly vibrating atoms, knocking against cooler less strongly vibrating atoms to pass the particle kinetic energy on. In metals, as well as this effect, the 'hot' high kinetic energy electrons move around freely to transfer the particle kinetic energy more efficiently to 'cooler' atoms.

  • Typical metals also have a silvery surface but remember this may be easily tarnished by corrosive oxidation in air and water.

  • Unlike ionic solids, metals are very malleable, they can be readily bent, pressed or hammered into shape. The layers of atoms can slide over each other without fracturing the structure (see below). The reason for this is the mobility of the electrons. When planes of metal atoms are 'bent' or slide the electrons can run in between the atoms and maintain a strong bonding situation. This can't happen in ionic solids.

  • For more on the properties and uses of metals see Transition Metals and Extra Industrial Chemistry pages and the note and diagram below.

 Note on Alloy Structure

(c) doc b

  1. Shows the regular arrangement of the atoms in a metal crystal and the white spaces show where the free electrons are (yellow circles actually positive metal ions).
  2. Shows what happens when the metal is stressed by a strong force. The layers of atoms can slide over each other and the bonding is maintained as the mobile electrons keep in contact with atoms, so the metal remains intact BUT a different shape.
  3. Shows an alloy mixture. It is NOT a compound but a physical mixing of a metal plus at least one other material (shown by red circle, it can be another metal e.g. Ni, a non-metal e.g. C or a compound of carbon or manganese, and it can be bigger or smaller than iron atoms). Many alloys are produced to give a stronger metal. The presence of the other atoms (smaller or bigger) disrupts the symmetry of the layers and reduces the 'slip ability' of one layer next to another. The result is a stronger harder less malleable metal.
  4. The main point about using alloys is that you can make up, and try out, all sorts of different compositions until you find the one that best suits the required purpose.
(thai) Doc Brown 's เคมี -- พันธะเคมี -- ส่วนติดโครงสร้างโลหะ 5 และคุณสมบัติ ส่วนที่ 5 โลหะ Bonding -- โครงสร้างและสมบัติของโลหะ (หน้านี้) * (portuguese) Doc Brown de Química - ligação química - Notas de Revisão Parte 5 Colagem Estrutura Metálica e Propriedades Parte 5 Metallic Colagem estrutura e propriedades dos metais elemento do modelo de ligação metal / ligas * propriedades físicas dos metais * (indonesia) Doc Brown Kimia - Ikatan Kimia - Catatan Revisi Bagian 5 Bonding metalik, Struktur dan Properties Bagian 5 Metalik Bonding - struktur dan sifat logam (halaman ini) bonding elemen logam model / paduan * sifat fisik logam *

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