These pages has been developed to help you understand and visualize how bonds form between atoms from atomic orbitals.
There are a number of theories to describe chemical bonding including Valance Bond Theory and Molecular Orbital Theory. In both cases the theory attempts to rationalize the geometry of a molecule based on how the bonds form. In both cases the idea of a chemical bond results from two (or more) atoms "sharing" electrons between them to complete the valance shell octet of the atom (i.e. a covalent bond). The atoms can share electrons when the atomic orbitals interact with each other, overlapping to produce a common orbital shared by both atoms and containing two electrons.
The strength of the interaction between two orbitals depends on:
- The relative energies of the two atomic orbitals which will combine to form the new "bonding" orbital. The closer the two atomic orbitals energies are to start, the stronger the interaction.
- The degree of overlap between two orbitals. For the two atomic orbitals to form a new bonding orbital they must merge together to form a common volume for the two electrons to share. Due to their relative shapes two "s" orbitals can overlap to a greater extent than two "p" orbitals. This means that sigma (σ) type bonds are stronger than pi (π) type bonds.
This orbital overlap can produce two unique types of bonds based on where the electron density of the resulting "bonding orbital" is located:
- Sigma (σ) bonds have the maximum electron density located along the internuclear axis.
- Pi (π) bonds have the maximum electron density located off the internuclear axis.
The reason atoms form bonds is that the molecule is more stable (lower in energy) than the isolated atoms. The "sharing" of electrons in a bond allow both atom to achieve a stable electronic structure, a full shell configuration similar to the noble gases (i.e. the so called "octet rule").
A guide to the site is listed below, and the buttons at the bottom of each page will provide sequential access.
The Wave Nature of Electrons
Sigma (σ) Bonds
Pi (π) Bonds
Electronegativity
Covalent Bonding
Polar Covalent Bonding
Ionic Bonding
Dipole Moments