Question

What is the quantization and additivity of charge?

Answer 1

Additivity:-
The charges adds up like real numbers, means if any system has n number of charges q1, q2, q3, qn then total charge of the system is 
q = q1 + q2 + q3 + ................ qn

Proper sign should be used while adding the charges.

Quantization:-
All free charges are integral multiples of a unit of charge,e,
where e = -1.602 × 10 -19 C
i. e., charge on an electron or proton
 
Thus if a body has charge q, mathematically.
q = ne
; n ∈ I

Answer 2

Quantization of charge---> Charge on a body is the integral multiple of electric charge. i.e q = ± ne… Additivity ---> if we consider a system of charges eg: q1 , q2 upto qn.. then total charge of the system is their sum… i.e q1 + q2 + …… + qn