A negative ion or anion is an electrically charged atom or group of atoms that are formed by gaining one or more electrons. Whereas a positive ion or cation is an electrically charged atom or group of atoms that are formed by losing one or more electrons. 
The losing and gaining all occurs on the outermost shell. 
        
             
        
        
        
Vol.250 before its to much pressure
        
                    
             
        
        
        
All scientists try to base their conclusions on data and measurements.
        
                    
             
        
        
        
Between atoms (one metall and one non metall) form an ionic bond(NaCl)
        
             
        
        
        
Answer: 
Calcium carbonate reacts with hydrochloric acid to form carbon dioxide gas. 2HCl (aq) + CaCO 3(s) CaCl 2 (aq) + CO 2(g) + H 2 O (l).