METALS
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METALS. Bonds and Properties. Alloys Pure Elements. Mr. ShieldsRegents 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

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METALS

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Metals

METALS

Bonds and

Properties

Alloys

Pure Elements

Mr. ShieldsRegents Chemistry

U09 L04


Metals

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

(* 2007 price)

Standard 400 oz ingots


Metals

Many Metals have high melting points

… But not all!

Where is the High Melting Pt. of W taken advantage of in your home?


More properties of metals

W

More Properties of Metals

Approx. 78% of the

Elements in the

Periodic Table are

Metals


Metal bonding

Metal bonding

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

-

+


Metals

Mobile metal electrons

Why can electrons in metals roam freely about?


Metal bonding1

Metal bonding

Metals exist in organized lattice structures similar to ionic

Compounds.

The difference is that

Adjacent atoms in the metal

Lattice are all the same.

Being in close proximity,

Outer Energy levels overlap.

AND…

Electrons in the outer

Valence shell can move freely through these overlapping

Energy levels.


Metals

Mobile Metal Electrons

Na 3s1 Na 3s1

Valence electrons move from

The valence shell of one atom

to the next

Overlapping orbitals


Metal bonding2

Metal bonding

“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

Neighbors.

- A metal bond is the attraction of metallic cations for

delocalized electrons


Metal properties

Metal Properties

  • It’s the sea of electrons

  • That give metals some

  • Of their unique properties.

  • Because they can move freely

  • From place to place they:

  • Conduct electricity

  • (a flow of electrons)

  • 2) Conduct heat

  • 3) Are malleable and ductile

  • 4) Have luster (e- absorbing then

  • releasing photons at the surface

How do electrons lead to these properties of metals?


Metals

+

Flow of electrons

e- 

 e-

Electrical Conductivity

-

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.


Malleability

Malleability

Metals and non-metals behave very differently when they are

Hit with a force such as a hammer.

Metals deform and

Non-metals shatter.

But Why?

Again it’s a

Consequence of

The Freely flowing

Electrons in metals


Metals

Metal

Non-Metal

Malleability

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

Non-metal, positive

And negative charges

align. This Results in a fracture due to the force ofrepulsion


Metals

Hardness & Strength

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

delocalized

- Chrome is very hard and has high strength


Metals

Hardness & 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)

AND

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)


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