Answer:
oxidation number is correct!! :)
Explanation:
 
        
             
        
        
        
Look at the protons and electrons and rememeber metals want to get rid of electrons to be perfect. Nonmetals are wanting to take in. Metals are negatives in electrons. Opposite for nonmetals. 
        
             
        
        
        
Answer:
The metric system goes by powers of ten, so it's very easy to measure. That would be the main advantage, measurements of ten. We can also say it's the most used measurement around the world, so all scientists have little to no conversion, but the main answer is probably the first one :)
 
        
             
        
        
        
Yeah...it should be out of your system by then