CHEMICAL BONDING Part 5
Structure and Properties of Metals
Brown's Chemistry Chemical Bonding GCSE/IGCSE/O/AS/A Level Revision Notes
DIAGRAMS of METAL STRUCTURES and their PROPERTIES EXPLAINED – Metallic bonding is described and the properties of
and alloys are described and explained using the giant metal lattice structure model which
is used to explain the physical properties of metals. The structure of
alloys is explained and why alloy metals are more useful than pure metals. These
notes on bonding in metals and explaining the structure and properties of
metallic structures are designed to meet
the highest standards of knowledge and understanding required for
students/pupils doing GCSE chemistry, IGCSE chemistry, O
Level chemistry, KS4 science courses and a basic primer for AS/A Level chemistry
courses. These revision notes on metallic bonding should prove useful for the
new AQA, Edexcel and OCR GCSE (9–1) chemistry science courses.
Part 1 Introduction
– why do atoms bond together? (I
suggest you read 1st)
Ionic Bonding – compounds and properties
Covalent Bonding – small simple molecules and properties
Covalent Bonding – macromolecules and giant covalent structures
Metallic Bonding – structure and properties of metals
Part 6 More advanced concepts for
advanced level chemistry (in preparation, BUT a lot on
intermolecular forces (intermolecular
bonding) in Equilibria Part 8)
metals be made more useful? (alloys of Al, Fe, steel etc.)
The physical and chemical properties of transition metals
– structure and properties of metals
bonding model of element & alloys * physical properties of
Its a good idea to have some idea
of where the metallic elements are in the periodic table
The black zig–zag line 'roughly' divides the metals
on the left from the non–metals on the right of the elements of the Periodic
Part of the modern Periodic Table
Pd = period,
Gp = group
metals => non–metals
that H does not readily fit into any group
Chemical Symbol eg 4Be
1 Alkali Metals
Gp 2 Alkaline Earth Metals
Gp 7 Halogens
Gp 0 Noble Gases
Chemical bonding comments about the
selected elements highlighted in white
e.g. the 'white' highlighted elements are
typical metals you are likely to have come across, either as a
pure metal or in an alloy mixture of metals – all the atoms are
held together by what is called 'metallic bonding'
– details of the bonding model below
Explaining the physical
properties of metals
All metals are lustrous and,
compared to non-metals, most metals are quite dense, hard (tough, high
tensile strength), with high melting/boiling points, though there notable
The strong metallic 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.
The stronger the attraction
between the atoms/ions in the giant metallic lattice, the more energy is
needed to weaken the force between them sufficiently to break the giant
lattice down in melting and completely overcome the attractive forces to boil the metal.
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.
The strong bonding in metals gives
them a high tensile strength, so alloys like steel are used in building
construction, car bodies etc.
Metals are good conductors of electricity
Why are metals good conductors
Metals are good at conducting electricity because
these 'free' delocalised 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.
Why are metals good conductors
The fact that metals are good at conducting heat 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.
metals, as well as this effect, the 'hot' high kinetic energy electrons move
around freely to transfer the particle kinetic energy more efficiently to
This is a faster process than the transferring heat by the
kinetic energy of atom vibration.
So, where a material needs to be
a good heat conductor, metals quite naturally are used to make everything
from radiators, cooking pans etc.
Its also hand that they are both
strong and high melting when used as a saucepan!
Typical metals also have a silvery surface
but remember this may be easily tarnished by corrosive oxidation in air and
Although many metals will
corrode (oxidise) in the presence of air (oxygen) and water, the strong
bonding prevents them dissolving in water or any other laboratory solvent.
When metals like sodium 'dissolve in water, they do so via a chemical
reaction forming a soluble compound (sodium hydroxide), and do NOT
give a solution of sodium metal.
Unlike ionic solids, metals are very
malleable - easy to bend or hammer into shape
Why are metals very malleable
and easily bent or pressed shaped?
Metals are be readily bent, pressed or hammered into shape
because the strong bonding is retained even when the metal is stressed (at least
up to a point!).
layers of atoms can slide over each other without fracturing
the structure (see below).
reason for this is the mobility of the electrons involved in the metallic
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 which
tend to be brittle and the layers of immobile ions fracture easily.
For more on the properties and uses of metals
see Transition Metals and Extra
Industrial Chemistry pages and the note and diagram below.
and may lead to
a very dangerous situation of mechanical failure of the structure.
Potential problems with metal
So it is important develop alloys which are well designed, well tested and
will last the expected lifetime of the structure whether it be part of an
aircraft (eg titanium aircraft frame) or a part of a bridge (eg steel
See notes on
Metals and Rust Prevention
on Alloy Structure via a very simplified 2D diagram
An alloy is a mixture of a metal with other
elements (metals or non-metals). Metals can be mixed together to make alloys to improve the metal's properties
to better suit a particular
purpose. An alloy mixture often has superior desired properties compared to
the pure metal or metals i.e. the alloy has its own unique properties
and a more useful metal.
- Shows the regular arrangement of the
atoms in a pure 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 ions of the giant lattice, so the metal object remains intact BUT the metal is
physically a different
- Shows an alloy mixture. Alloys
are NOT compounds but a physical mixing of a metal plus at least one other
material (shown by red circle).
- The other material can be another metal e.g. nickel
or manganese added to iron in steel, or a
non–metal e.g. carbon, and it can be
bigger or smaller than the iron atoms.
- Many alloys are produced like
this to give
a stronger metal.
- The presence of the other atoms (smaller or
bigger) disrupts the symmetry of the layers and this distortion reduces the 'slip
ability' of one layer to slide next to another layer of metal atoms.
- The result is a stronger
harder less malleable metal, but one better suited to most
- 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 in terms of tensile/compression strength, malleability,
electrical conductivity or corrosion resistance etc.
- Most metals in everyday use in the
home or industry are alloys.
- This is because pure metals such as
copper, gold, iron and aluminium are too soft for most uses and
so are mixed with other metals to make a far more useful harder
- The are hundreds of alloys of
steel made by alloying iron with other metals to increase the
strength or anti-corrosion properties of the metal.
- Steel is used in building and
bridge construction, car bodies, railway lines and countless
other objects that need to have a high tensile strength.
- Pure metals can be either too
soft (e.g. like copper or tin) or too brittle (e.g. like zinc)
to be used directly and are therefore often alloyed to make
superior metals like brass or bronze.
- The properties of metals are
readily matched to a particular use e.g.
- Aluminium alloys are strong and
light (relatively low density for a metal), they do not corrode
easily and so are used in aircraft construction, greenhouse
frames and not as expensive as titanium alloys.
- Cooking pans made of stainless
steel are good conductors of heat, strong with good
anti-corrosion properties and steel has a high melting point.
- Copper is malleable and ductile,
easily drawn out into wire, an excellent conductor of
electricity, and so is widely used in electrical circuitry.
Steel alloys of varying strength and
anti-corrosion properties are used in thousands of products and
constructions e.g. reinforcing rods in concrete buildings, bridge
girders, car engines, domestic appliances from washing machines to
electric kettles, saucepans, tools like chisels, ship hulls and
superstructure, very hard drill bits,
- For more on specific metals and
alloys see my notes on Transition
Revision notes information to help revise KS4 Science
Additional Science Triple Award Separate Sciences GCSE/IGCSE/O level
Chemistry Revision–Information Study Notes for revising for AQA GCSE Science, Edexcel
GCSE Science/IGCSE Chemistry & OCR 21st Century Science, OCR Gateway Science WJEC/CBAC
GCSE science–chemistry CCEA/CEA GCSE science–chemistry
(and courses equal to US grades 8, 9, 10) basic aid notes for GCE Advanced
Subsidiary Level AS Advanced Level A2 IB Revise AQA OCR Edexcel Salters CIE,
CCEA/CEA & WJEC advanced level courses for pre–university students (equal to US grade 11 and grade 12
and Honours/honors level courses)
WHAT NEXT? – other pages to do with metals