Integrated SequencePhysics Chemistry Organic Biology

Web Resources

HyperPhysics - Covalent Bonds

Purdue University - The Covalent Bond
Portal to a number of clear, well-illustrated tutorials on covalent bonding concepts.



  click if a link is broken



Special points of emphasis

Work, Energy, and Power

Electricity

The Chemical Bond

Thermochemistry

At this stage in the MCAT course, we are carefully studying the nature of chemical bonds in themselves. In a few weeks, we will be studying chemical reactions in which old bonds are broken and new bonds formed. Let us preview an important conceptual cluster, the internal energy changes involved in chemical bond formation that will be so important to our understanding of the thermochemistry of reactions later.

The internal energy change of two atoms undergoing bond formation involves a decrease in electrostatic potential energy. The total energy of the bound molecule, with the atoms separated by the bond distance, is less than the energy of the system with the atoms fully separated. Why is this so?

Imagine bond formation.

As electrons within nonbonded atoms form molecular orbitals, the nuclei are drawn inward along the bond axis and internal energy decreases. Let us say that again. Try to picture it in your mind. As the bonding electrons form molecular orbitals, their presence in the internuclear space draws the nuclei inward, an electrostatic potential energy decrease. Unlike charges are being drawn together, the negatively charged electrons in the bonding orbital with the positively charged nuclei on either side.

This is a blended classical/quantum description designed to help you conceptualize bond formation. Most chemical reactions involve the breaking of old bonds (internal energy increase) coinciding with new bonds forming (internal energy decrease). Whether the system has lost or gained internal energy depends on whether the stronger bonds are the bonds broken or the bonds formed.

Don't blow past this. Think about electrostatic potential energy. Think about bond formation as a trip two atoms take down into a potential energy well. How deep is the well? That's how strong the bond is, i.e. how much energy the system loses when the bond is formed.








The WikiPremed MCAT Course is a free comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum.

Please read our policies on privacy and shipping & returns.  Contact Us.
MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course.


Creative Commons License
The work of WikiPremed is published under a Creative Commons Attribution Share Alike 3.0 License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions. You can use the resources here for commercial or non-commercial purposes, but please give attribution and a link to the production credits and edit history of the resource. For the works here which began as my individual work, please attribute "John Wetzel, an author at wikipremed.com".