Question

if the symbol for cobalt Co wewre written as CO what would be wrong with it

Answer 1

ya symbol of cobalt is written as Co,and CO represents carbon monoxide

Answer 2

Every element's name must be distinct to that they can be identified correctly. As mentioned by you, Co which is Cobalt cannot be written as CO as this would be chemical formula of Carbon Monoxide where C is Carbon and O is oxygen. And, in Co, the makes one word, i.e. Cobalt.