The Lewis structure for carbonyl sulfide (OCS) can be drawn by following these steps:
- Determine the total number of valence electrons: Carbon (C) has 4, oxygen (O) has 6, and sulfur (S) has 6. Therefore, the total is 4 + 6 + 6 = 16 valence electrons.
- Place the least electronegative atom in the center. In this case, carbon is the central atom, with oxygen and sulfur on either side.
- Connect the atoms with single bonds. This uses up 4 of the 16 valence electrons (2 for each bond).
- Now distribute the remaining electrons to complete the octets of the outer atoms. Place 6 electrons around oxygen and 6 around sulfur. After this step, you will have used 16 electrons (4 for bonds + 12 for outer atoms).
- Since carbon is left with only 4 electrons in its outer shell, we need to create a double bond between carbon and oxygen to satisfy the octet rule. This means removing one lone pair from oxygen and forming another bond with carbon. This gives oxygen a total of 8 electrons and carbon also achieves a full octet.
The final Lewis structure places a double bond between carbon and oxygen (C=O) and a single bond between carbon and sulfur (C-S). Thus, the Lewis structure looks like this:
O S || || C
In summary, the Lewis structure for OCS shows a linear arrangement where oxygen has a double bond to carbon, and carbon has a single bond to sulfur. This configuration fulfills the octet rule for all three atoms involved.