If there’s one “mental model” to keep in your head as you begin to learn organic chemistry, it’s this one.
Opposite charges attract, like charges repel
It all comes from Coulomb’s law, which is taught in most introductory physics courses. The attraction between opposite charges (as well as the repulsion between like charges) is inversely proportional to the square of the distance between them.
Everything you’re going to learn in organic chemistry is ultimately a consequence of this.
Here are some important examples:
- Structure. Methane (CH4) is tetrahedral because the electrons (“like” charges) in each of the C–H bonds repel each other, and a tetrahedron is the shape which maximizes their distance apart. Borane (BH3) is trigonal planar because this is the structure that orients the three B–H bonds the furthest distance apart from each other.
- Bonding. Chemical bonds are a consequence of the attraction between (negative charged) electrons existing between two (positively charged) nuclei.
- Boiling points reflect the degree to which molecules are attracted to one another, which depends on electrostatic interactions between molecules.
- Reactivity. Essentially every reaction you will learn about will involve interactions between species with high electron density (negative charge) with species of low electron density (positive charge). Opposite charges attract.
Thanks for reading!