1. Covalent Bonding
a few extra concepts

2. Coordinate Covalent Bond
bond formed when:
2 atoms share pair electrons but
both electrons donated by same atom
many polyatomic ions have coordinate covalent bonds
must be able to recognize them

3. H .. + H : N : H H+1 .. oh oh – no electrons at all!
2 non-bonding electrons just hanging around
will join together in a bond and form an ion

4. Ammonium, NH4+1 +1 H ..
H : N : H .. H
both electrons in this bond were donated by the N atom in ammonia NH4

5. .. + H : O : H H+1 .. Hydronium, H3O+1 2 pairs of non-bonding e-
zero electrons

6. Hydronium, H3O+1 +1 H
both electrons are provided by the oxygen atom in water (H2O) ..
H : O : H ..

7. NETWORK SOLIDS
carbon and silicon form extensive networks, similar to a crystal lattice
different physical properties than molecular compounds:
hard rather than soft (except graphite)
high mp & bp, high Hf & Hv
similar physical properties than molecular cmpds:
non-conductors

8. NETWORK SOLIDS: Carbon
most covalent substances are molecular
carbon forms 4 bonds with 4 other C atoms
allows C to build up extensive network
ex: diamond, graphite
strong covalent bonds
hold atoms together

9. Diamond Structure

10. Network solids: Silicon
silicon can also form network solids
ex: quartz (SiO2)
quartz has very complicated crystal structure