New Way Chemistry for Hong Kong A-Level Book 1 1 Chapter 10 Metallic Bonding 10.1Metallic Bonding 10.2Metallic Radius 10.3Factors Affecting the Strength

New Way Chemistry for Hong Kong A-Level Book 1

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Chapter 10Chapter 10Metallic BondingMetallic Bonding

10.110.1 Metallic BondingMetallic Bonding

10.210.2 Metallic RadiusMetallic Radius

10.310.3 Factors Affecting the Strength ofFactors Affecting the Strength of

Metallic BondingMetallic Bonding

10.410.4 Metallic Crystals Metallic Crystals


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The electron sea model of bonding in metals

• The structure of metal consists of a giant structure of cationic lattice immersed in a sea of mobile valence electrons.

• The electrostatic attraction between the delocalized electron cloud and the metallic ions is the metallic bonding.

10.1 Metallic Bonding (SB p.248)


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Metallic radius (r) is defined as half of the internuclear distance between atoms in a metal crystal.

Metallic radius (r) is defined as half of the internuclear distance between atoms in a metal crystal.

10.2 Metallic Radius (SB p.249)

Atoms in a metallic crystal


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The metallic bond increases with:

1. decreasing size of the metal atom (i.e. the atomic/metallic radius);

2. increasing number of valence electrons of the metal atom.

10.3 Factors Affecting the Strength of Metallic Bonding (SB p.249)

Metals with small and highly charged cations form stronger metallic bonds


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Effect of number of valence electrons on metallic bond strength

Metal Number of valence electrons(s)

Melting point (o

C)

Sodium

Magnesium

Aluminium

1

2

3

98

650

660


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Effect of metallic radius on metallic bond strength of Group 1A metals

Metal Metallic radius (mm) Melting point (oC)

Lithium

Sodium

Potassium

Rubidium

Caesium

0.152

0.186

0.231

0.244

0.262

180

98

64

39

29


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Closed-packed Structure10.4 Metallic Crystals (SB p.250)


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(a) normal side view (b) exploded view (c) a unit cell

Co-ordination no. = ?Co-ordination no. = ? Empty space = 26%Empty space = 26%

10.4 Metallic Crystals (SB p.252)

Hexagonal close-packed structure


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(a) normal side view (b) exploded view (c) a unit cellCo-ordination no. = ?Co-ordination no. = ? Empty space = 26%Empty space = 26%


Cubic close-packed / Face-centred cubic structure


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Open Structure



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(a) normal side view (b) exploded view (c) a unit cell

Empty space = 32%Empty space = 32%


Body-centred cubic structure


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The crystal structures of the solid metal elements



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The END

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New Way Chemistry for Hong Kong A-Level Book 1 1 Chapter 10 Metallic Bonding 10.1Metallic Bonding 10.2Metallic Radius 10.3Factors Affecting the Strength