The Basics
- Valence Shell Electron Pair
Repulsion
- electron repel each other
- electrons in molecule will arrange themselves so that they are as far apart as possible
because of this repulsion
- helps explain 3-D molecular structure
Types of Electrons Found in Molecules
- bonding pairs
- two electrons involved in a bond.
- represented by two dots or a line between two atoms
- can be a single bond (2 electrons), double bond (4 electrons), or triple bond ( 6 electrons)
- also called a shared pair
- Nonbonding pairs
- pairs of electrons not involved in bonding
- also called lone pairs or unshared pairs
- Single electrons
- Not mentioned in much detail in our course
- nonbonding, unpaired electrons
General Formula Representations
In order to easily represent many different shapes of molecular compounds, the following symbols will be used, regardless of the elements composing the compound.
A= central atom
- least electronegative element in compound
X = atoms or groups of atoms attached to central atom
E = nonbonding pair
e = lone nonbonding electron
Electron Domains
- Each area where electrons exist will be referred to as a domain
- A domain can have 1, 2, 4, or 6 electrons
- A single bond, double bond, triple bond, or unshared pair all count as 1 domain.
- You can determine the number of domains in a molecule by totalling the number of atoms ( or groups of atoms) attached
to the central atom and the number of unshared pairs of electrons surrounding the central atom.
- You will need to draw a dot diagram to determine the number of unshared pairs
- Since all domains are arranged to the central atom, they will arrange themselves in a manner to maximize the
distance between the electron pairs.
- the degree of repulsion can be indicated by the following formula
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