Answer:
Both are pure substances and a compound
 
        
             
        
        
        
Answer:
an energy level represents the three dimensional space surrounding nucleus where electrons are most likely to be.
Explanation:
 
        
             
        
        
        
Where's the list? If you show it maybe I can help
        
             
        
        
        
True I believe because plants require gases which they take from the air.