The Lewis structure for the sulfate ion (SO42-) represents the arrangement of electrons in the molecule. To draw this structure, we start by determining the total number of valence electrons available.
1. **Count valence electrons**: Sulfur (S) is in group 16 of the periodic table and has 6 valence electrons. Each oxygen (O) also has 6 valence electrons, and since there are four oxygens, that gives us a total of 24 valence electrons from oxygen. The sulfate ion carries a -2 charge, meaning we add 2 more electrons to our total. So the total is:
- 6 (from S) + 24 (from 4 O) + 2 (for -2 charge) = 32 valence electrons.
2. **Draw the skeletal structure**: Place the sulfur atom in the center with the four oxygen atoms surrounding it. Connect each oxygen to the sulfur atom with a single bond initially. This uses 8 electrons (2 electrons per bond) out of the 32 we have, leaving us with 24 electrons.
3. **Distribute remaining electrons**: Start placing the remaining 24 electrons around the oxygen atoms to satisfy their octet. Each oxygen needs 8 electrons, and since each O is already bonded to S with one bond, we can place 6 more electrons on each one, giving us:
- 4 O atoms × 6 electrons = 24 electrons used.
4. **Check the structure**: Each oxygen now has a full octet (8 electrons) while the sulfur atom only has 8 electrons as well. However, sulfur can expand its octet. To represent the bonding more accurately, we can convert one of the lone pairs from each oxygen into double bonds with the sulfur atom. This leads to a structure where two of the sulfate’s oxygen atoms will be double-bonded to sulfur while the other two are single-bonded. This gives a more stable configuration.
5. **Resonance structures**: Since we can have different combinations of which oxygens have double bonds, sulfate has multiple resonance structures. However, all configurations ultimately reflect the same overall distribution of electrons.
In conclusion, the Lewis structure for SO42- can be simplified to show sulfur double-bonded to two oxygen atoms and single-bonded to the other two, with each bond adequately indicating the sharing of electrons.