A lewis structure is simply an electronic configuration of our atoms, our molecules and compounds. So let's begin by using formaldehyde. So we're going to have this compound that's compared composed of one carbon, one oxygen and two h atoms. Now we're going to draw the lewis down structure for our formaldehyde. So our first step is to count the number of balanced electrons. Balanced electrons, once again, of those electrons that come from the outermost shells of our atoms.