Kwame Nkrumah University of
Science & Technology, Kumasi, Ghana
Metallic Bonding
Lecture 3
Dr. Eric S. Agorku
Senior Lecturer, Inorganic/Bioinorganic/Coordination Chemistry
Chemistry Department
Metallic Bonding
• Strong forces of
attraction are
responsible for the high
melting point of most
metals.
• They cannot undergo
ionic or covalent
bonding.
Why?
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Electronic Configurations
Element
Sc
Ti
V
Cr
Mn
Configuration
[Ar]3d14s2
[Ar]3d24s2
[Ar]3d34s2
[Ar]3d54s1
[Ar]3d54s2
All are willing to give
electrons but none willing
to accept
[Ar] = 1s22s22p63s23p6
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Oxidation States of Transition Elements
Sc
Ti
+3
V
Cr
Mn Fe
Co
Ni
Cu
+1
+1
+2
+2
+2
+2
+2
+2
+2
+2
+3
+3
+3
+3
+3
+3
+3
+3
+4
+4
+4
+4
+4
+5
+5
+5
+5
+6
+6
+6
Zn
+2
+4
+7
3/7/01
Ch. 24
11
loss of ns e-s
loss of ns and (n-1)d e-s
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Metallic Bonding
• Metal is a lattice of positive
metal 'ions' in a 'sea' of
delocalized electrons.
• The physical properties of metals
are the result of the
delocalization of the electrons
involved in metallic bonding.
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Metallic Bonding
❑ The chemical bonding results
from the attraction between
metal cations and the
surrounding sea of electrons
❑ Vacant p and d orbitals in metal's
outer energy levels overlap, and
allow outer electrons to move
freely throughout the metal
❑ Valence electrons do not belong
to any one atom
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Metallic Bonding
❑ This is called the electron sea
model.
❑ Electron Sea Model: metal
atoms contribute their valence
electrons to form a “sea” of
electrons.
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Packing in Metals
Model: Packing uniform,
hard spheres to best use
available space. This is
called closest packing.
Each atom has 12
nearest neighbors.
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Metal Alloys
❖Substitutional Alloy:
some metal atoms
replaced by others of
similar size.
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Metal Alloys
❖Interstitial Alloy:
Interstices (holes) in
closest packed metal
structure are occupied
by small atoms.
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Properties of Metals
❑ Metals:
➢ conduct heat
➢ conduct electricity
➢ generally high melting points and
high boiling points
➢ strong/hard
➢ malleable (can be hammered or
pressed out of shape without
breaking)
➢ ductile (able to be drawn into a
wire)
➢ metallic cluster
➢ opaque (reflect light)
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Properties of Metals
Conduct heat and electricity
• Solid and liquid metals conduct heat and electricity.
• The delocalized electrons are free to move in the solid lattice.
• These mobile electrons can act as charge carriers in the conduction of electricity or
as energy conductors in the conduction of heat.
• Good conductors attracts their outer electrons the least (low I.E)
Generally high melting points and high boiling points
•
In general, metals have high melting and boiling points because of the strength of
the metallic bond.
The strength of the metallic bond depends on the:
o number of electrons in the delocalized 'sea' of electrons.
(More delocalized electrons results in a stronger bond and a higher melting point.)
o packing arrangement of the metal atoms.
(The more closely packed the atoms are the stronger the bond is and the higher the
melting point.)
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Properties of Metals
Malleable/ductile
• The delocalized electrons in the 'sea'
of electrons in the metallic bond,
enable the metal atoms to roll over
each other when a stress is applied.
Opaque
Photons of light do not penetrate very
far into the surface of a metal and are
typically reflected, or bounced off, the
metallic surface.
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Group Assignments
Group 1
1. Differentiate between inorganic and bioinorganic chemistry.
2. What are essential elements?
3. Classify essential elements in terms of:
i. Bulk structural elements
ii. Macrominerals
iii. Trace elements
iv. Ultratrace elements
Group 2
1. What are the criteria for essential elements in relation to
biological systems. Explain the concept of essentiality.
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Group Assignments
Group 3
1. Describe the role of essential elements in biological systems (both
plants and animals).
Group 4
1. What is a heavy metal? Describe the toxicity of some metals (Cu,
Pb, Hg, As) in humans
Group 5
1. Give examples of anticancer metallotherapeutics and
2. Draw their structures and uses.
Group 6
1. Give examples (10) of metal proteins with four subunits in the
quaternary structure and discuss their roles in biological systems.
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