GCSE-IGCSE-KS4 Ionic, Covalent, Polymer and Metallic Bonding Revision notes at Doc Brown's Chemistry Clinc. docb4

docb4_72bond5 updated April 6th 2008

KS4 SCIENCE - Additional & Applied Chemistry help AQA GCSE Science - Chemistry CCEA GCSE Science - Chemistry Edexcel GCSE 360Science - Chemistry OCR GCSE 21st Century Science Suite - Chemistry OCR GCSE Gateway Science Suite - Chemistry OCR GCSE Applied Science - Chemistry (double award) WJEC GCSE Science - Chemistry

Doc Brown's Chemistry Clinic

GCSE-IGCSE KS4 Science-CHEMISTRY and AS (basic) Chemistry Revision-Information Notes on

The Structure and properties of substances - Ionic, Covalent & Metallic Bonding

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)

Associated notes on other web pages:

Atomic Structure notes & diagrams including electron arrangements.

Models and properties of Gases, Liquids and Solids.

A brief survey-summary of the Periodic Table including electronic structure and formula patterns.

How to work out formula of ionic or covalent compounds without going through some demanding electronic thinking is described in the valency section on the "Elements, Compounds and Mixtures" page and it is followed by a section on naming compounds.

GCSE BONDING m/c QUIZZES: Foundation or Higher

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Part 5. METALLIC BONDING - structure and properties of metals

metal bonding model element/alloys * physical properties of metals

BONDING IN METALS

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.

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

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).
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.
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.
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.

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Online free help resources for Key Stage 4 AQA, Edexcel, OCR, CIE GCSE IGCSE BTEC Science, GCE, AS, A2 Advanced subsidiary Chemistry A levels, IB Diploma and US K12 (K-12 grades) courses and examinations and revising for the various syllabuses and specifications. Exploring the site for lessons, plans, ideas for projects and coursework, professional development. Through hard work the site has been built up over the course of many years with no need of special pc software except FrontPage and Hot Potatoes (uvic) for quizzes and worksheets. It is used in the classroom, home learning-tutoring-schooling and guidance, private tuition, school retakes revision. Whether you are a teacher/tutor teaching, a student studying, using the pages as self-study guides for your science-chemistry studies etc. etc. I hope the site supports your endeavour. 15-12-07 © Dr W P Brown