 Custom Search
The Nature of Chemical Bonds: A bond can be described as a mutual attraction between 2 nuclei and electrons. This system will try to maximize attraction (opposite charges attract), while minimizing repulsion (repulsion occurs between particles of the same electrical charge)
Notice the electrons repel each other, but more importantly the nucleus of each atom does also. The nucleus usually carries a charge of more than 1+ (unless it is hydrogen) and this repulsion keeps the atoms apart. Now look at the attraction between the negative electrons and positive nucleus. This attraction keeps the atoms close together. The balance that occurs from this keeps the atoms together. Here is the tough part to understand, the atoms are constantly moving apart and coming back together (like clapping your hands). The bond length and this diagram is an average of the possible positions the atoms are in. Chemical Bond Energy Here is a different way to describe a chemical bond using energy. You should be aware that nature tends to favor systems with lower energy. Notice below that the 2 hydrogen atoms have more energy as lone atoms than they do if the were bonded together as H-H. Nature favors lower energy so the atoms will bond and give off energy when it bonds.
Forming bonds releases energy (exothermic). H + H à H-H + energy Breaking bonds absorbs energy (endothermic). H-H + energy à H + H *** Think about how you separate water from a wet towel. You heat it and the water leaves, and the towel is now dry. Wet towel à Dry towel Water-Towel + Heat à Towel + water The bond is broken with heat. Bonding, Energy and Nuclear Distance Now let’s discuss how the energy changes with a change in nuclear distance. Remember lower energy is favorable, when using this diagram.
Let’s start on the right side of this diagram. The atoms are very far apart. Almost no attract between the nuclei and the electrons of the other atom. Long distance relationships don’t work. Now look at the left side. These atoms are incredibly close, too close for comfort. The repulsion of the nuclei drive them apart. This energy is much higher than if the atom were completely separated, so this will not last. Finally, look at the dip. That is a situation where the energy is lower. Lower energy is favorable in nature. This situation is just right. Not to far apart, but not to close together. Attraction is maximized and repulsion is minimized. The bottom of the dip will give is the average bond length and average bond energy. ***Remember atoms are always moving, closer together and further apart, so we use averages.**** |
.
