1. 12 Chemistry Atomic Structure and Bonding CR 07
Types of solids
Solids are classified according to
their properties
Properties of solids depend on:
Particle type
Bonding within and between the particles
12 Chemistry Atomic Structure and Bonding CR 07

2. 12 Chemistry Atomic Structure and Bonding CR 07
Ionic Solids
Ionic crystals are made of ions
which sit in a 3D network of
positive and negative ions.
12 Chemistry Atomic Structure and Bonding CR 07

3. Properties of Ionic solids
Are very hard but can be cleaved
12 Chemistry Atomic Structure and Bonding CR 07

4. Ionic solids properties cont’d
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)
12 Chemistry Atomic Structure and Bonding CR 07

5. Ionic solids properties cont’d
Soluble in polar substances
Polar solvents overcome the electrostatic forces between ions
12 Chemistry Atomic Structure and Bonding CR 07

6. 12 Chemistry Atomic Structure and Bonding CR 07
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)
12 Chemistry Atomic Structure and Bonding CR 07

7. 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
12 Chemistry Atomic Structure and Bonding CR 07

8. 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 Chemistry Atomic Structure and Bonding CR 07

9. 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
12 Chemistry Atomic Structure and Bonding CR 07

10. 12 Chemistry Atomic Structure and Bonding CR 07
Polar molecules
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. *be able to explain
12 Chemistry Atomic Structure and Bonding CR 07

11. 12 Chemistry Atomic Structure and Bonding CR 07
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
12 Chemistry Atomic Structure and Bonding CR 07

12. Properties of metallic solids
Malleable and ductile due to non-directional metallic bonds
Good conductors of heat and electricity due to density and mobile electrons
High melting and boiling points due to strong metallic bonds
Not soluble
12 Chemistry Atomic Structure and Bonding CR 07

13. 12 Chemistry Atomic Structure and Bonding CR 07
The strength of metallic
bonds varies and so
consequently the melting
and boiling points of
different metals varies.
12 Chemistry Atomic Structure and Bonding CR 07

14. Giant covalent network solids
are made of atoms arranged in
covalent networks with strong
covalent bonds (very strong inter-
particular bonds) between them
12 Chemistry Atomic Structure and Bonding CR 07

15. Types of network solids
Linear chains
2-D layers
3-D covalent network
12 Chemistry Atomic Structure and Bonding CR 07

16. Types of network solids
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
12 Chemistry Atomic Structure and Bonding CR 07

17. 12 Chemistry Atomic Structure and Bonding CR 07
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
12 Chemistry Atomic Structure and Bonding CR 07

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.
12 Chemistry Atomic Structure and Bonding CR 07

19. 12 Chemistry Atomic Structure and Bonding CR 07
Graphite structure
12 Chemistry Atomic Structure and Bonding CR 07

20. 12 Chemistry Atomic Structure and Bonding CR 07
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.
12 Chemistry Atomic Structure and Bonding CR 07

21. Properties of covalent network solids
Covalent network solids have
High MP (strong covalent bonds hold atoms in place)
Do not conduct electricity (all electrons held in covalent bonds)
Very hard/strong
Insoluble in any solvent
12 Chemistry Atomic Structure and Bonding CR 07