Metallic bonding
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Transcript Metallic bonding
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valence electrons detach from individual
atoms since metals contain only 1-3 valence
electrons and a low ionization energy
bonding is non-directional
no particular electron is confined to a particular
metal cation
leaves a close packed lattice of cations in a sea of
delocalized negative electrons
the electrostatic attraction between the
cations and sea of electrons holds the metal
together
electrons act as a "glue" giving the substance a
definite structure
Characteristics
strength of a metallic bond depends on…
1. number of delocalized valence electrons
more delocalized electrons = greater
electrostatic attraction (higher MP)
2. size of cation’s charge
stronger the charge = greater electrostatic
attraction (higher MP)
3. ionic radius
when the metallic atom radius increases,
the sea of negative electrons becomes
farther away and harder for nuclei to hold
on to
therefore, melting point decreases as you go
down the periodic table
the delocalized nature of the bonds, make
it possible:
conduct electricity
for the atoms to slide past each other
this means metals are malleable and ductile
hammered into thin sheets or shapes without
breaking
drawn into wires
ionic compounds would crack
contain more than one metal and have enhanced
properties such as
greater strength
the presence of different atoms disturbs the regular lattice
and hinders movement
resistance to corrosion, enhanced magnetic
properties, and greater ductility
examples
steel
Fe and C -- high tensile strength but can rust
brass
Cu and Zn – looks cool!
gold alloy, dental amalgam, and so on…
metals are essential part of the world
economy
reinforcement of concrete, wires, cars,
pipes…
traded as commodities
most common is iron which is in steel