23.1 Metals and
Metallurgy
Transition Metal Chemistry
Fred Omega Garces
Chemistry 201
Miramar College
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Transition Metals, Properties
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Earth -Stratosphere - Lithosphere
Earth radius
(6370 km, 10192 mi)
Deepest well - 8 Km (12.8 mi)
mines - 4 Km (6.4 mi)
Mesosphere!
Stratosphere!
Troposphere!
Lithosphere
Most of our metals found in
concentrated deposits
known as Ore
Ore - mixture of materials
Metallurgy - Science of extracting
metals and the studying and
manipulation of their properties.
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History Timeline
History is divided by composition of tools
used in that periodStone Age, Bronze Age, Iron Age, ...
• Today iron is not the dominant metal for industry
anymore.
• A jet engine is composed of Ti, Ni, Cr, Co, Al,Nb, Tl
• Similarly the best golf clubs is made out of Ti, Zr,
B or some alloy.
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Metallic Bonding
Physical Properties of Metals
Important physical properties of pure metals: Malleable,
ductile, good conductors, and feel cold.
Most metals are solids with the atoms in a close packed
arrangement.
In Cu each atom is surrounded by 12 neighbors.
There are not enough electrons for the metal atoms to be
covalently bonded to each other.
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Properties of Metal
Theories describing properties & behavior.
VBT (electron - sea model)
Electron-sea model proposes:
-Delocalized model for electrons
in a metal.
MO (Bond Theory)
Delocalized model by
Overlap of atomic orbitals
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VBT (electron - sea model)
Valence orbital overlap such that e- are free to
migrate.
The metal nuclei exist in a sea of electrons.
No e- localized between any two metal atoms.
Therefore, the electrons can flow freely.
Without any definite bonds,
metals easy to deform (and are malleable and ductile).
High e- conductivity an heat capacity (heat conductor)
Electron Sea model: metal bonds parallel number of
valence electron, the greater the valence electrons, the
greater the bond strength.
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Draw Back of VBT
Problems with the electron sea model:
• As the number of electrons increase,
the strength of bonding should increase
and the melting point should increase.
But:
• Group 6B metals have the highest melting points (center
of the transition metals).
Sc g Cr g Zn
Increase melting point ...highest for Cr.
...then decrease melting point, …contrary to Theory.
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MO (band Theory)
MO is a more qualitative approach. This
theory treats bonding in terms of bonding and
antibonding. Classic MO Theory.
Consider Chromium:
[Cr] = 4s1 3d5 Bond Order = 6
Electron fills bonding orbital, highest bond order is when
all bonding orbital are occupied and there are no
antibonding contributions.
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MO for transition metal
MO explains bond strength trend
Sc BO = 1 to Cr BO = 6
e-fill bonding orbital (low BO to high BO)
Cr
BO = 6
to Zn
BO = 1
e- fill anti-bonding (high BO to low BO)
e- free to roam under thermal conditions
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MO For Insulator
Next available orbital not available for e-,
therefore e- are immobilized.
Large gap
therefore ecan’t be
promoted
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Transition Metals and Valence eTransition metals characterized by incomplete d-orbitals
d-orbitals lead to multiple oxidation states.
Zeff slowly increase
resulting in lower oxidation states for later transition elements.
(Since Zeff larger for latter transition metals, it is more difficult
to remove e- therefore latter elements can’t attain high Ox.
number.)
Sc (+3) ...Cr
(+ 2...+6)...Mn (+2...+7)....Zn (+3)
Note Zn has the smallest ionic radii, and largest Zeff
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Similar trend going down
Period
(2nd and 3rd row
transition metal)
Note: Going down pt,
expect Atomic
radii to decrease:
Sc<Y<La
For Ti, Zr, Hf, this
pattern doesn’t
follow trend
Ti < Zr = Hf. Why?
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Atomic Radius
The size systematically
decreases going across
the periodic table until
the 8B family, and
then the atomic radii
increases again.
Transition Metals, Properties
January 13
Lanthanide contraction
• Between La and Hf,
Z = 57 to 72, and the number of
protons increases resulting in
increase in Zeff
The increase in Zeff for Hf, offset
the increase in n when going from Zr
to Hf, therefore Zr and Hf are
about the same size.
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Other Properties
Some miscellaneous properties for the fourth
period transition elements.
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Magnetism
Presence of unpaired of e- lead to
interesting magnetic properties
diamagnetic, no unpaired e-, actually is repelled
by magnetic. field
paramagnetic- presence of unpaired e-. will be
influence by strong magnetic. field.
Attraction
ferromagnetic - also presence of unpaired eexcept that in there are domains in solid that
permanently align selves in presence of
magnetic field.
Ferromagnetic 1•106 more magnetic than
paramagnetic material
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Metals,
Metalloid &
Nonmetals
The properties of
elements in terms
of their metallic
character.
The d-block elements
lose their valence selectrons when they
form compounds.
Moreover, most of them
can also lose a variable
number of d-electrons,
and hence show variable
valence. Variable
valence makes these
elements useful as
catalysts and, in biomolecular chemicals
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