This week's science tutor video is a foundation for understanding the chemistry of inorganic matter, along with its implications for biology. I cover three types of chemical bonds, but I also get into the Van der Waals interaction because it happens to be very cool.
If you're not familiar with orbitals and electron shells, you should scroll down past the video and watch the tutorial on orbitals and electron shells first.
If you need some science tutoring on electron shells, watch this video first:
All known life depends on a fairly short list of complex chemical reactions, and most of these reactions are combinations of some basic processes. Most of these chemical processes are tied in with the types of chemical bonds that are formed between atoms and molecules.
In other words, there's a simply hierarchy: Atoms -> molecules -> chemical bonds and chemical reactions -> metabolism, respiration, reproduction, etc. Chemicals combine to form organelles and cells. Cells make up tissues, which in turn make up organs. Organs interact to form organ systems, and collectively these organ systems constitute an organism. Like you and me.
But it all starts with chemistry, so pay attention.
Covalent bonds are formed when two or more atoms share their electrons.
Ionic bonds form when one atom gives up an electron to another atom, creating ions. A positively charged ion (ie, one that lost an electron) is a cation, while a negatively charged ion is an anion. Cations and anions bind together to create salts. Salts are very strong when they are dry, but water interferes with the attraction between positive and negative charges. This is why salts dissolve in water.
Hydrogen bonds are weak. They allow molecules (usually macromolecules in biology) to form loose, temporary bonds. The best and most important example would be the hydrogen bonds between base pairs in DNA. Since the bonds are weak, it is easy for a section of DNA to zip and unzip.
Did you know that when a gecko climbs up a wall, the hairs on its feet are actually forming a chemical bond with the wall? This is the Van der Waals effect. Post something in the forum, if you have any questions.