Fill in the coefficients that will balance the following reaction: a0ki + a1pb(no3)2 → a2pbi2 + a3kno3

The answer 

the main rule
A   B
A is the reactants  and B the products of a reaction
the number of atome of the elements of A must be equal to the number of atome of the elements of B
in our case
to balance the equation
a0 KI + a1 Pb(NO3)2 → a2 PbI2 + a3 KNO3
 2KI      +   Pb(NO3)2  →     PbI2 +     2KNO3
proof

A (reactants ) B (products)

 2KI means  2K,   2I             PbI2 :   2I,  2KNO3:  2K ( K and I are balanced) 
 Pb(NO3)2:
1 Pb, 2 NO3                         PbI2 and 2KNO3:  
                                             1Pb and  2 NO3 (Pb and NO3 are balanced)

finally 
 a0= 2,  a1= 1, a2= 1, a3=2                            
            

Hello thereone of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description? answer: atomic mass  was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.