Question

how many electrons will constitute 2x10^-6 C of charge 

Answer 1

Q = ne
2×10^-6 = n×1.6×10^-19
n = 1.25×10^13  (n = number of electrons) 

Answer 2

Charge on 1 electron = 1.6 X 10^-19 C                  (elementary charge)
Total Charge = 2 X 10^-6 C

Therefore Q = ne                (Quantisation of charge)
Here n = number of electron, e = elementary charge = 1.6 X 10^-19, Q = Total Charge

2 X 10^-6 C = n (1.6 X 10^-19C)
n = 2 X 10^-6 C/1.6 X 10^-19C
n = 1.25 X 10^13 electrons