C₃H₈ contains 3 carbon atoms and 8 hydrogen atoms.

Now, each carbon atom has 4 electron and each hydrogen atom has 1 electron each.

So, in total 3×4 + 1×8 = 12 + 8 = 20 electrons.

And, 1 single bond = 2 electrons.

∴ 10 single bonds.

There now plot the electrons on the atoms as shown, and then jin the single bonds.

This is the final structure of propane i.e. C₃H₈