Chemistry · Structure Of Atom · NEET
It means electric charge is not smooth or continuous. It comes only in fixed small packets. The smallest packet is the charge of one electron, e = 1.6 x 10^-19 coulomb. Any object's total charge is a whole-number multiple of this packet. You cannot have a bit of charge smaller than e. This is why we write q = ne.
n is a whole number: 1, 2, 3, 4 and so on (an integer). It counts how many electron-charges are present. If a drop has 3 extra electrons, then n = 3 and q = 3e. n can never be a fraction like 1.5 or 2.7. This is the key point NEET tests.
No. Because n must be a whole number, q can be 1e, 2e, 3e, but never 1.5e or 2.5e. If a question gives you a charge that is NOT a whole-number multiple of 1.6 x 10^-19 C, that value is not possible for a real charged body. (Note: quarks have fractional charge inside the nucleus, but they are never found free, so at NEET level the smallest free charge is e.)
In his oil-drop experiment, Millikan measured the charge on many tiny oil drops. Every single drop had a charge that was a whole-number multiple of 1.6 x 10^-19 C. For example, drops had charges like 1e, 2e, 3e, but never something in between. Since e was always the common building block, he concluded charge is quantised and q = ne.
The smallest free charge is the charge of one electron (or one proton), e = 1.6 x 10^-19 C. A neutral body has n = 0. A charged body has at least n = 1. So no charged object can carry less than e.
Both. A proton carries +e and an electron carries -e (same size, opposite sign). Removing electrons leaves a positive charge (still a multiple of e), and adding electrons gives a negative charge. Either way, the total is always n times e, so q = ne holds for positive and negative charges.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
q = ne, where q is the total charge, e = 1.6 x 10^-19 C is the charge of one electron, and n is a whole number (integer).
Robert Millikan, through his famous oil-drop experiment, measured the charge on the electron and showed all charges are whole-number multiples of e.
NEET often gives a charge value and asks if it is possible, or asks how many electrons were transferred (n = q/e). Knowing q = ne with integer n lets you solve these fast.
Yes. n = 0 means no extra charge, so the body is neutral (q = 0). For a charged body, n is 1 or more.
Yes. A proton has charge +e. Removing electrons gives a positive charge that is still a whole-number multiple of e, so q = ne works for both signs.
