A model is a simplified view of a complex system. Useful models are consistent with experimental evidence and have predictive power.
Over the years, a complex model for chemical bonding has developed that enables rationalisation of a large amount of experimental evidence. In the teaching of chemical bonding it is commonplace to use the simplest form of the model that explains the particular aspect of bonding that is of interest and to introduce additional complexity only when required. This is the approach that will be used in this module.
Introducing the model
Bonding involves the valence electrons (The electrons on an atom that are in the outermost shell and in unfilled subshells. Bonding involves valence electrons.) on the bonded atoms.
The number of valence electrons for an atom is the same as last digit of the Group number in the periodic table.
Each dot in a valence electron diagram represents a valence electron for the atom having the symbol shown. The valence electron diagrams for some elements in their ground state (The lowest energy arrangement of electrons in the available orbitals on an atom.) show that some electrons paired.
The first step in gaining an understanding of chemical bonding is to recognize the appropriate valence electron diagram for an atom and thus how many of the electrons on each of the bonded atoms are involved in bonding.
Note: Electrons are shown in four groups around the atom with pairing of electrons increasing across a period. The reason for the four groups and the increase in pairing will become apparent in your future studies of chemistry.
Over the years, a complex model for chemical bonding has developed that enables rationalisation of a large amount of experimental evidence. In the teaching of chemical bonding it is commonplace to use the simplest form of the model that explains the particular aspect of bonding that is of interest and to introduce additional complexity only when required. This is the approach that will be used in this module.
Introducing the model
Bonding involves the valence electrons (The electrons on an atom that are in the outermost shell and in unfilled subshells. Bonding involves valence electrons.) on the bonded atoms.
The number of valence electrons for an atom is the same as last digit of the Group number in the periodic table.
Each dot in a valence electron diagram represents a valence electron for the atom having the symbol shown.
| Group | Group | Group | |
 |  |  |  |
 |  |  | |
 | |||
 |
The first step in gaining an understanding of chemical bonding is to recognize the appropriate valence electron diagram for an atom and thus how many of the electrons on each of the bonded atoms are involved in bonding.
Note: Electrons are shown in four groups around the atom with pairing of electrons increasing across a period. The reason for the four groups and the increase in pairing will become apparent in your future studies of chemistry.