Answer:
25 valence electrons.
Explanation:
Hello!
In this case, based on the attached picture, you can see that the chlorate ion has three oxygen atoms and one chlorine ion, whereas you can see there is a coordination bond (two arrows) from chlorine to oxygen which means that oxygen receives two electrons from chlorine in order to complete its octet and to allow chlorine to not exceed the octet. It means there is another oxygen completes its octet via the Cl=O bond and the the last oxygen is negatively charged because it is missing one bond to attain its octet even thought chlorine actually completes its octet.
Therefore, this ion has seven valence electrons from chlorine and 18 valence electrons from the three oxygen atoms, which means it has 25 valence electrons overall.
Best regards!
