Week 18 in the Ron Paul Curriculum Chemistry course was all about Structural Formulas. All four lessons were spent learning about and writing out structural formulas, and I must say it is quite fun when you have gotten so good at writing it all out without help or reference.
Lesson one of week 18 started off with how to write a skeletal structure of a compound. Writing out a compound this way shows only the elements and not their valence electrons. There are certain elements that act as central atoms in chemistry bonds and form many covalent bonds. These include the elements carbon, silicone, nitrogen, phosphorus, and oxygen. It takes a while to get the hang of writing out the skeletal structure of every different compound, but with practice you learn how to do it. After the skeletal structure is written out, you envision all the valence electrons. Writing them all out helps you know if you miss any when placing them around the skeletal structure. But before you do that, you have to figure out the number of covalent bonds. To do this you use the equation S = N – A.
S = N – A
Where A is the total number of valence electrons in the compound.
Where N represents the number of electrons needed by each atom in the compound.
Once you have written out the skeletal structure and placed all the valence electrons, you turn the structure into a Lewis Formula by converting the electron bond pairs to dashes.
The next three lessons of week 18 continued to go over writing structural formulas and Lewis structures, as well as more practice problems.
Structural Formula Steps:
- Write the skeletal structure of the compound.
- Imagine or write down all the valence electrons of the compound.
- Determine the number of covalent bonds using the S = N – A equation.
- Draw the covalent bonds between the atoms.
- If you fall short, try adding double or triple bonds in order to satisfy the central and surrounding atoms desire for an octet electron configuration.