Transcript Slide 1
Topic: Metallic Bonding
Do
Now:
Name
as many properties of ionic compounds
you can without looking (then look to make
sure you got them all
METALS
Alloys
Pure Elements
Bonds and
Properties
REVIEW:
Some Properties of Metals
LUSTER/Shiny
DEFORMABILITY
Malleable & Ductile
Good CONDUCTIVITY :
HEAT AND ELECTRICITY
Solid at at STP
(except Hg)
Lose e- to form (+) ions
Low IONIZATION ENERGY
(lowest: Fr)
Low ELECTRONEGATIVITY
(lowest: Fr)
Many metals have high luster
Hmmm….
How much is this
shiny Gold worth !?
400 ounces (27.5lbs)
$1738.35 / ounce
$695,340.00 per bar
12 ars =
$8,344,080.00
Many Metals have high melting points
Metallic vs Ionic Bonding
• Both bond types due to: electrostatic attraction
• Metallic bonding: different from ionic bonding
Ionic bond: transfer electrons from one atom
to another
Metal bonds: electrons ROAM FREELY from
one metal atom to next
sea of mobile electrons
accounts for properties of metals
Metallic bonding
Metals:
form organized lattice structures
similar to ionic cmpds
adjacent
atoms in metal lattice are all same
close proximity
of atoms allows
Na 1s1
Na 1s1
outer energy levels
to overlap
So…
electrons in outer valence shell can move freely
through these overlapping energy levels
=
“sea of mobile electrons”
Metal bonding
Freely moving electrons:
called “delocalized” electrons
allows (+) metal cation to form
Delocalized electrons move freely throughout
metal from one cation to next
creates what’s called “the sea of mobile
electrons”
This sea of electrons:
• binds each metal cation to
each neighbor cation
• this creates the metal bond
Metal Properties
sea of mobile electrons gives metals some of
their unique properties
since electrons move freely from place to
place they:
•
conduct electricity (a flow of electrons)
●
conduct heat
●
are malleable and ductile
●
have luster
Electrical Conductivity
+-
e-
Flow of electrons
e-
Free flow of electrons through the metal
e- flow from metal through metal wire
towards (+) charge; then flow from (-)
terminal back into metal
Malleability
Metals & non-metals behave very differently when hit with a
force such as hammer
Metals DEFORM:
Non-metals SHATTER
Metals have free
flowing electrons
& nonmetals do not!
Metals DEFORM:
Ionic Cmpds SHATTER
If force applied to metal:
•some metal atoms shift away from force & free electrons
simply bond the newly overlapping metal ions together
•metal is deformed but
shift doesn't change
metal atoms
If force applied to
Ionic compound:
•like charges align (+) & (+)
(-) & (-) which results in
shattering due to force of repulsion
Deformation of Metals
Deformation of Metals
As # of electrons that can be delocalized ↑ so does:
Hardness and Strength
EXAMPLES:
• Na has one valence electron that can be delocalized
- is relatively soft ( can be cut with a butter knife)
• Mg has two electrons that can be delocalized so:
- can still be cut but is much harder than Na
• Transition metals have varied # of e-'s that can be
delocalized
- Chromium is very hard and has high strength
Alloys
mixture
of elements that have metallic
properties
mixture can be adjusted to get desired
properties
can be substitutional
(elements of the same size)
or interstitial
(elements that are different sizes)
Brass:
Common alloys
Cu & Zn
Bronze: Cu, Sn & Al
Pewter: Sn, Pb & Cu
Solder: Pb & Sn
Rose gold: Cu & Al
White gold: Au & Ni,
Pd or Pt
Sterling silver: Ag &
Cu
Steel: C & Fe
Stainless steel: Cr & Ni