Explanation:
both iron and sulphur in FeS2 undergo a change in oxidation state. 
 O2°	-->2O degree2- Total decrease = 2×2=4
 So, 4FeS2+11O2 --> 2Fe2O3+8 SO2
 Hence, balanced 
 
        
             
        
        
        
Iodine is one of seven elements that usually form as diatomic molecules. These other "diatomics" are 

 and 

. They typically bond to themselves.
Iodine has seven valence electrons. Using valence shell electron pair repulsion (VSEPR) theory, we can predict the Lewis dot structure for 

. We see there are fourteen electrons, and we can make a covalent bond, leaving three lone pairs on each atom. The bond replaces two electrons, so the number of electrons shared is two.
 
        
        
        
Mg will lose 2 valance electrons to obtain octet