1. Solid state Chemistry (CHEM 422)
Prof. Ayman Nafady
King Saud University
Chemistry Department

2. Week 1-2: Lectures Solid State Chemistry
It is an in-depth examination of the principles and concepts underlying the synthesis, structure, bonding, reactivity, and physical properties of solid state materials.

5. Solid State
Solid is a physical state of matter which is characterized by strong intermolecular force of attraction and least intermolecular distance.
The constituent particles are held together with strong forces which make this physical state compact and non-compressible.
The constituent particles of solids cannot move from their position but can vibrate at their mean position.
They are held together with strong intermolecular forces such as ionic or strong covalent bonding.
Because of these strong forces, they have definite shapes and volumes.
On the basis of ordered arrangement of particles, solids can be classified as
crystalline and amorphous solid.   

7. Crystalline solids
Crystalline solids are classified according to their properties and structure into four Categories. These include:
(1) Ionic solids
(2) Molecular solids
(3) Metallic solids
(4) Covalent solids

8. (1)-Ionic Solids
Ionic solids: are made of ions which sit in a 3D network of positive and negative ions.
Are very hard but can be cleaved

9. Ionic solids properties
Do not conduct electricity (no free ions or electrons)
except when molten or aqueous (as ions are free to move)
High melting point and boiling point
because of very strong inter-particular attractions (electrostatic attractions)
Soluble in polar substances
Polar solvents overcome the electrostatic forces between ions

10. (2)-Molecular solids Molecular solids are made of molecules.
There are strong bonds within the molecules
(strong intra-molecular forces)
but weak attractions between the molecules
(weak inter – molecular forces)
Properties of Molecular solids:
Have low melting and boiling points
because of weak inter-molecular forces
The molecules themselves are not broken up – just moved apart from each other when molten

11. Molecular solids properties cont’d
Do not conduct electricity - even when molten (no free ions or electrons)
Insoluble in water and other polar substances
Few are solid at room temperature – eg. Dry ice

12. Polar and non- polar particles
Molecular solids can be made from polar or non polar molecules.
The inter- molecular forces between non-polar molecules are only weak van der Waals forces.
Van der Waals attractions are the weak electrostatic attractions between atoms of different EN
Polar molecules have dipoles and so have slightly stronger attractions between them meaning that the melting point of a polar molecular solid is a little higher because more energy is needed to overcome the slightly stronger forces.

14. (3)- Metallic solids
Metals are made of positive nuclei held together by a sea of de-localised electrons (e- do not belong to any one nucleus)
Forces between the particles are strong metallic bonds
Malleable
It can be hammered or bent into
different shapes without breaking
Ductile
They can be drawn or pulled
into a long strand of wire without breaking
due to non-directional metallic bonds
Atoms can slide over each other

15. Properties of metallic solids
Good conductors of heat and electricity due to density and mobile electrons can transmit energy quickly
High melting and boiling points due to strong metallic bonds
Not soluble in any solvent
The strength of metallic bonds varies and so consequently the melting and boiling points of different metals varies.

16. 4- Network solids 1-D sloids (Linear chains)
Made up of atoms connected by covalent bonds
The intermolecular forces are covalent bonds as well.
Characterized as being very hard with very high melting points and being poor conductors.
1-D sloids (Linear chains)
are infinitely long linear chains held together by van der Waals
Properties:
Low MP but longer chains have higher MP than shorter ones
Do no conduct electricity
Soft and flexible
Eg. Polythene, rubber, plastics

17. 2. 2-D Layers held together by weak van der Waals forces.
Graphite is made of layers of covalently bonded C atoms.
The layers are held together by weak van
der Waals forces and have delocalised
electrons between them. *this is very
unusual and graphite is the only non-
metal to conduct electricity

18. Properties of Graphite
Conducts electricity because of delocalised electrons
High melting point – C atoms are held by strong covalent bonds
Soft and greasy texture (used as a lubricant) as the layers slide past each-other easily – weak van der Waals forces.
Graphite has only 2-D hexagonal structure and therefore is not hard like diamond.

19. 3. 3-D covalent network solids
are made of atoms held together by strong covalent bonds. Diamond and silica (silicon dioxide) are two examples of covalent network solids.
Diamond is the strongest substance known to man.

21. Irregular shape

22. Amorphous Solids Properties
No definite melting point - no crystal lattice to break
Exhibit characteristic glass transition temperature, Tg
Flow when subject to pressure over time
Isotropic i.e. same properties in all direction

23. Amorphous materials