1. Factors affecting metallic bond strength Metallic crystal structures
F.6 Metallic Bond
Factors affecting metallic bond strength
Metallic crystal structures

2. Factors affecting metallic bond strength: 1. Atomic (metallic) radius
2. No. of valence electrons
Decrease in radius
Na Mg Al
371K K K K
336K Melting
Rb Point (K)
312K
Increase
In radius

3. Metallic bonding
is an electrostatic attraction between sea of electrons and positive ions.
Metallic radius:
as half the internuclear distance between two atoms in a metallic crystal

4. Metallic bonding
Factors affecting the strength of metallic bonding:
1. number of valence electrons (outermost electrons / bonding electrons) and charge on cations. e.g. b.p. : Al > Mg > Na
2. metallic radius. e.g. b.p. : Li > Na > K
i.e. larger no. of valence electrons, smaller metallic radius will result in stronger metallic bonds.

5. Close-packed structure Open structure
Metallic bonding
10.4 Metallic crystals
Close-packed structure
Open structure
68 % of space occupied by atoms/ co-ordination no. = 8
74 % of space occupied by atoms / co-ordination no. = 12
Hexagonal close packed structure:“abab”
Cubic close-packed structure:”abcabc”
Body center cubic structure

6. Close-packed Structure (2 types)
Open Structure (1 Type)
Close-packed Structure (2 types)

7. Unit Cell Co-ordination number: 8 Number of atom in a unit cell:
Open Structure: Body-centered cubic
Co-ordination number: 8
Number of atom in a unit cell:
1 + 8 ( 1/8) = 2
Unit Cell

8. 10.4 Metallic crystals
Open structure

9. Iron and all Group I metals
Open Structure: Body-centered cubic
Examples:
Iron and all Group I metals

10. abababab….. hexagonal Co-ordination number: 12
Close-Packed Structure: Hexagonal close-packed
abababab…..
Co-ordination number: 12
(6 in its own layer, 3 in the layer above and 3 below.)
hexagonal

11. 10.4 Metallic crystals
co-ordination no. = 12
Hexagonal close-packed structure:“abab”

12. Close-Packed Structure: Hexagonal close-packed
Example:
Magnesium

13. abcabcab….. also called face-centered cubic Co-ordination number: 12
Close-Packed Structure: Cubic close-packed
abcabcab…..
Co-ordination number: 12
(6 in its own layer, 3 in the layer above and 3 below.)
also called face-centered cubic

14. 10.4 Metallic crystals
co-ordination no.
= 12
Cubic close-packed structure:”abcabc”

15. Copper, Gold, Silver Examples:
Close-Packed Structure: Cubic close-packed
Examples:
Copper, Gold, Silver

16. 10.4 Metallic crystals
“abab” and “abcabc”

17. Tetrahedral hole
Octahedral hole

18. 10.4 Metallic crystals