When we draw Lewis structures, we'll follow four steps. First, we'll calculate the total number of valence electrons in the compound. Second, we'll draw the structure with only single bonds between atoms, indicating which atoms are bonded. Third, we'll satisfy the octet rule by adding lone pairs of electrons, starting with peripheral atoms. Peripheral atoms are only bonded to one other atom, whereas central atoms are bonded to two or more other atoms. If we run out of lone pairs and not all of our atoms are satisfied, we'll create double or triple bonds using the lone pairs we've already distributed until all of our atoms are satisfied. If we have electrons left over and all of our atoms are satisfied, we can put the extra electrons on the central atom if it's in the third row or below of the periodic table. We'll see examples like this after we talk about the exceptions to the octet rule. And finally, we can use formal charge to evaluate the Lewis structure. We'll incorporate this last step with more complicated Lewis structures after discussing formal charge. Let's begin with a basic Lewis structure. Our first step is to sum our valence electrons. We have one phosphorus atom with five valence electrons and three fluorine atoms with seven valence electrons each. Since this is a neutral molecule, we do not need to adjust our number of valence electrons for a charge. Adding these together, we have 26 valence electrons. Next, we'll draw the structure with only single bonds. In simple covalent compounds, the central atom or atoms are generally listed first, so we'll put phosphorus in the middle with our three fluorine atoms attached by single bonds. These three bonds have used up six electrons, so we have 20 electrons left. Next, we'll satisfy the octet rule by adding lone pairs of electrons. We'll start with the peripheral fluorine atoms. Each fluorine atom wants eight electrons, but it currently has just one bond, which contains two electrons. So each fluorine atom wants an additional six electrons. Adding these lone pairs, we'll have used up another 18 electrons, and we have two valence electrons left over. Now that our peripheral atoms are satisfied, we can look at our central atom, phosphorus. Phosphorus wants just two more electrons, so we can add our last lone pair to phosphorus. In this Lewis structure, all of our atoms are satisfied, so we don't need to create any double or triple bonds. We have also used up all of our lone pairs of electrons, so we don't need to add any additional lone pairs to our central atom. Since we haven't introduced formal charge yet, we'll skip our last step for this example.