Correct Answer  Option 3 : (y  x) × 1.6 × 10
19 C
CONCEPT:
Electric Charge
 It is defined as the intrinsic property of certain fundamental particles like electrons, proton, etc, due to which they produce electric and magnetic effects.
 Types of electric charge

Positive charge: A body having a deficiency of electrons.

Negative charge: A body having an excess of electrons.
 Properties of electric charge
 Like charges repel and unlike charges attract each other.
 A charge is a scalar quantity.
 If a system contains a number of point charges, then the total charge of the system is obtained simply by adding all the charges algebraically.
 A charge is always quantized.
 A charge will always remain conserved.
 A charge is always associated with mass.
 The unit of charge is the coulomb.
⇒ 1 coulomb = charge on 625 × 1016 electrons
EXPLANATION:
Given x = number of electrons, and y = number of protons
Quantisation of charge:
 Experimentally it is established that all free charges are integral multiples of a basic unit of charge denoted by e.

This basic unit of charge is the charge that an electron or proton carries.
 Thus charge q on a body is always given by:
⇒ q = ne
Where n = integer and e = 1.6 × 10^{19} C (Charge on one electron or one proton)
So the charge on the body due to x number of electrons,
⇒ q_{e} = x × (1.6 × 1019 C)
And the charge on the body due to y number of protons,
⇒ qp = y × (1.6 × 1019 C)
 If a system contains a number of point charges, then the total charge of the system is obtained simply by adding all the charges algebraically.
 So the total charge on a body is given as,
⇒ q = q_{e} + q_{p}
⇒ q = (y  x) × 1.6 × 10^{19} C
 Hence, option 3 is correct.