METALS. Bonds and Properties. Alloys Pure Elements. Mr. Shields Regents Chemistry U09 L04. Recall that many metals have high luster. Like GOLD!. Hmmm…. How much is this shiny Gold worth ??. 400 ounces (27.5lbs) $647 / ounce* $258,800 per bar 12 bars = $3,105,600
Mr. Shields Regents Chemistry
How much is this
Gold worth ??
400 ounces (27.5lbs)
$647 / ounce*
$258,800 per bar
12 bars =
(* 2007 price)
Standard 400 oz ingots
… But not all!
Where is the High Melting Pt. of W taken advantage of in your home?
The bonding in metals is very different from that of an ionic bond
In an ionic bond there is a transfer of electrons from one
atom to another
But in metal bonds electrons ROAM FREELY from one metal
atom to the next.
It’s these freely roaming electrons that account for many of
the properties of metals
Why can electrons in metals roam freely about?
Metals exist in organized lattice structures similar to ionic
The difference is that
Adjacent atoms in the metal
Lattice are all the same.
Being in close proximity,
Outer Energy levels overlap.
Electrons in the outer
Valence shell can move freely through these overlapping
Na 3s1 Na 3s1
Valence electrons move from
The valence shell of one atom
to the next
“Delocalized” electron leaves behind centers of temporarily
Positive Metal Cations.
The delocalized electron then
Moves freely through the
Metal from one Cation
To the next.
This creates what is called
“the Sea of Electrons”
This Sea of Electronsbinds each metal Cation to all its
- A metal bond is the attraction of metallic cations for
How do electrons lead to these properties of metals?
Flow of electrons
Free flow of electrons through the metal
Electrons flow from the metal through the metal wire towards the + charge
Electrons then flow from the negative terminal back into the metal they
originally came from.
Metals and non-metals behave very differently when they are
Hit with a force such as a hammer.
Metals deform and
Again it’s a
The Freely flowing
Electrons in metals
When a force is applied to a metal some of the metal atoms shift away from the force.
But the free electrons simply bond the newly overlapping
Metal ions together.
The metal has
Been deformed but
The shift is not
Of any consequence
When a force is
Applied to the
And negative charges
align. This Results in a fracture due to the force ofrepulsion
As the number of electrons that can be delocalized
Increases so does Harness and Strength
Na has one s electron that can be delocalized
- its relatively soft & weak ( can be cut with a butter knife)
Mg has two electrons that can be delocalized
- so its much harder than sodium but not a lot of strength
Transition metals have several s and d electrons that can be
- Chrome is very hard and has high strength
In General as you move left to right across a period
The strength and hardness of the metallic bond increases (as
long as the # of s and d electrons that can be delocalized inc.)
(for ex: Fe 2-8-14-2 is harder than Cu 2-8-18-1 because Cu’s d
Orbitals are all filled so they are not available for bonding. Fe
Does have d orbitals that can participate)
In general as you move down a group the strength of the
Metallic bond and the hardness decreases because the
Delocalized e- are farther from the pos. cation (Cu is a harder
metal than Au)