So firstly, in organic chemistry... There are compounds which are complex/time consuming to write using the full form of the Lewis Dot Structure. So we chemists, (Lol, I'm not a chemist.) tend to shorten it by simply drawing lines.
That is propane or C\(_3\)H\(_8\). Some of you maybe thinking, how is that propane?
Simply, we assume that all the vertices are carbons. And if there are no specific bonds to those vertices then we assume that the carbons are bonded to hydrogens. And remember, a carbon atom can have up to four bonds.
So now, using those two assumptions... Here we have the expanded propane.
Now notice, it is indeed C\(_3\)H\(_8\).
The reason why we shorten it is because when it gets to more complex compounds. It would be tiresome to draw all the lines and etc.
So this is how organic chemists write compounds in these shortened form of the Lewis Dot Structure. Soon, I shall get into the nomenclature of compounds and the functional groups.
If you have any questions, comments, queries etc. Feel free to comment. ^^ Well, that was quite short. Hahha...