So here if we take a look at this example, it says based on your understanding of the polyatomic oxy anions provide the structure for the thiocyanate ion. Alright, so we know that our cyanate ion is OCN-. And remember we've come across this prefix of file before.
Remember, when we have this prefix of Thio, it means that we're going to replace an oxygen with a sulfur. So if we're dealing with thiocyanate, that means we're going to replace one oxygen with a sulfur. In this case, we only have one oxygen, so it's just going to get replaced with a sulfur.
So this becomes SCN- and in the rest of it stays the same S-. So our cyanate is one of our other polyatomic ions of OCN-. That was the key to knowing what thiocyanate looks like. Remember thiol just means replace an oxygen with a sulfur while maintaining everything else about the polyatomic ion the same.
So our answer would be SCN-.