It's cl-1 It's electron configuration is 2.8.7. And it need 8 electron for the 3rd shell to be balanced. So you ionize Cl by adding another electron. But why is it Cl-1? Well, because Cl's electron configuration is 2.8.7. As I mentioned... When you have balanced it to 2.8.8. You need to -1 to make … Read more