Anhydrides :
Anhydrides are binary substances or compounds that are the result of a nonmetal with oxygen.
I leave you 2 steps to make the anhydrides:
1: To make anhydrides, write your nonmetal symbol followed by oxygen.
2: The oxidation numbers must be the same and for this the exchange of oxidation numbers or valence between its non-metallic element and Oxygen is used.
Examples of anhydrides:
1: Chlorous anhydride
Keep in mind that when it ends in OSO we look for its valence, which in this case would be +3.
2: Iodic anhydride
We take into account its symbol that in this would be me and to solve it we must look for its valence that in this case ends in ICO which is already known that its ICO valence is +5.
3: Per bromic anhydride
We take into account its symbol, which in this case would be Br, and to solve it we must find its valence, which in this case ends in ICO, which is already known to have an ICO valence of +7.
The Table of metals and non-metals is attached.