CHEMICAL BONDING Metallic Bonding

Overview

Bonding Ionic Covalent MetallicStructure Giant

ionicSimple

molecularGiant

covalentGiant

MetallicExample Sodium

chlorideWater Diamond Iron

Bonding and structure explains the properties of a substance!

Think about metals!

What are some properties of metals?

Shiny surfaces?

Can it be bent?

Strong materials?Can it stretch?

Good electrical conductor?

Good heat conductor?

Physical Properties of Metals

Appearance Can have shiny surfaces

Physical state Usually solid Density Usually high

M.P. & B.P. Usually highEase of shaping Malleable and ductile

Heat and electrical conductivity

Good

Exception??

Metals Have Giant Structures

Atoms are packed closely together in an orderly manner.

"Giant" implies that large but variable numbers of atoms are involved.

Metallic Bonding

Each metal atom gives up its valence electrons to form positive ions.

These electrons no longer belong to any metal atom they are delocalised.

They move freely in the space between the metal ions.

‘Sea’ of electrons

The number of delocalized electrons depends on the number of metal ions.

It does not mean an excessive number of electrons.

Metallic Bond: The Definition

A metallic bond is…the (electrostatic) force of attraction between

positively charged metal ions and negatively charged free or

mobile(delocalized) electrons.

Physical Properties: Explanation

Solid, high density Metal ions are packed tightly in layers.

High M.P. and B.P. Metal ions and electrons are held together by strong

metallic bonds. Application? Exception? +

-+ + + + +

+ + + + + +

+ + + + + +

+-

-

-

-

----

-

-- -

-

---

-metal ion

free electron

Physical Properties: Explanation

Malleable and ductile When a force is applied to a metal, the layers of

atoms can slide over each other easily.

The ‘sea’ of electrons holds the atoms together so that it does not break.

Physical Properties: Explanation

Good electrical conductor Metals conduct

electricity when solid and when molten.

Due to the movement of the delocalized electrons.

Application?

Physical Properties: Explanation

Good heat conductor Due to the movement of delocalized electrons When heated, the delocalized electrons gain more

energy and move faster, colliding with neighbouring electrons. Heat is transferred in these collisions.

Application?

Ask yourself!

1. List the physical properties of metals.2. Explain why metals can be malleable or ductile3. Explain how a metal conduct electricity

So, what have you learnt?

The structure of a metal a lattice of postive ions in a ‘sea of electrons’

Metallic bonding: the electrostatic force of attraction between positive metal ions and negative electrons.

Physical properties of metals and their explanation