Beryllium, Magnesium, Calcium....etc have two valence electrons
        
             
        
        
        
Number 4 is 
-Oxidation occurs at the anode, while reduction occurs at the cathode. Recharging a battery involves the conversion of electrical energy to chemical energy. During recharging, there is movement of electrons from an external power source to the anode, and on the other side electrons are removed from the cathode.
        
                    
             
        
        
        
D. a compound can only be separated into its components by chemical means
        
                    
             
        
        
        
Answer: because they take a lot of tie to form