1. Chemical Bonding

2. Chemical bonds
understanding of chemical bonds central to understanding of chemistry
new arrangement of electrons and nuclei has less energy than before bond
localisation of negative electrons holding together two adjacent positive nuclei
(see EvansChem)

3. Chemical bonds DElectronegativity 0 increasing high
Type of bonding non-polar polar ionic
covalent covalent
Melting & boiling usually low
points high
Electrical never when molten
conductivity or in solution
Sodium hydride and water DEN between atoms = 1.3

4. Covalent Bonding
e.g. 2 hydrogen atoms forming an hydrogen molecule

5. Covalent Bonding When the hydrogen molecule forms
There is a merging/overlap of electron orbitals
The atoms take up a position at a distance such
that the forces of repulsion and attraction balance.
This distance is known a the bond length (ro)
A certain amount of enthalpy is released into the surroundings
The energy required to break one of these bonds is known as
The bond entahlpy or bond dissociation energy

6. Number of electron pairs shared
Covalent Bonding
Number of electron pairs shared
Type of covalent bond
Example 1
Single
Hydrogen 2
Double
Oxygen 3
Triple
Nitrogen

7. Lewis electron-dot diagrams
Diagrams show bonding and non-bonding
electrons in molecules
e.g. H : H or H x H
H Cl H x Cl