Repeat the same for another Oxygen atom as well. However, if you shift electrons from the Oxygen atom and form a double bond with the Sulfur atom, it might solve our problem. So this is not the correct Lewis Structure.

So if you add up the charges, it is 4(-1)+ (-2) = -6, which is technically wrong as we have a charge of -2 on this ion.īesides, the Sulphur atom cannot have a higher negative charge than the Oxygen atom as it is less electronegative than it. Using this formula, you will find out that when there are four single bonds in this molecule, each Oxygen atom has a charge of -1, and the Sulphur atom has a charge of -2. You can either use our Formal charge calculator to find the charges on the atoms or use the following formula:į.C = Valence electrons – Nonbonding pairs of electrons * ½ bonding pairs of electrons Now doing this, you might wonder that this is the correct way to present the Lewis Structure, but it is suggested to calculate the formal charges to do so. Start putting these electrons around the Oxygen atom, as Sulphur has shared four electrons with the Oxygen atoms. Placing four single bonds will use eight valence electrons out of 32, which means we are only left with 24 valence electrons now. So place a pair of electrons between each Oxygen and Sulphur atom to show a single bond. Now that you have the arrangement of the atoms in the molecule, we can look at the bonding of atoms.Īs mentioned above, each atom will try to have eight valence electrons in its outer shell to attain a stable structure. So place a Sulfur atom in the center and Oxygen atoms around it. So as a result of this Sulphur atom will take the central position, and all the Oxygen atoms are arranged around it. In SO42-, if you compare the electronegativities of Sulphur and Oxygen atoms, Oxygen is more electronegative than Sulphur atoms. This doesn’t apply to Hydrogen atoms, as these atoms never take the central position. To determine which atom takes the central atom, always remember that the less electronegative atom takes the central position, and more electronegative atoms are arranged around it. Here as we already have the total number of valence electrons, we can start by determining the central atom.

Arrangement of the atoms in the molecule.

There are some exceptions to this rule certainly, but the majority of the atoms follow this rule.įor determining the Lewis Structure for SO42- molecule, we need to know the feeling: Generally, while forming bonds with other atoms, every atom tries to follow an octet rule that states that an atom must have eight valence electrons to attain a stable structure. Apart from that, it also helps to know the molecular shape, polarity, and other properties of the molecule. The Lewis Structure of any molecule helps to understand the bonding of atoms in the structure.

Hence there are a total of 32 valence electrons for the Sulfate ion. Total valence electrons for SO42- = 6 + 6(4)+2 = 32 Here we have one Sulphur atom and 4 Oxygen atoms, and both these elements belong to the same group and have six valence electrons in their outermost shell.īut as there is a -2 charge on this molecule, it means that it accepts two additional electrons to attain a stable structure, and hence we have to consider these electrons as well. These electrons are the ones that are present in the outermost shell of the atom and participate in forming bonds. Concluding Remarks SO42- Valence electronsįor determining the Lewis Structure for any molecule, we first need to know the total number of valence electrons.

So2 molecular geometry name