(i) The number of electrons in any orbit can be determined by the general formula 2(n²), where n = 1, 2, 3….. and so on. Here ‘n’ represents the number of shell like 1 for the first, 2 for the second and so on.

(ii) So to determine the maximum number of electron in any orbit we can use the formula 2(n²).

(iii) For first orbit n = 1 maximum electron are 2(1²) = 2 electrons.

(iv) Similarly if we take third or fourth shell n = 3 or 4, maximum electrons will be 2(3²) = 18 and 2(4²) = 32.

(v) For n = 4 the maximum electrons come out to be 32 and for n = 3 it is 18 but that is not possible as the repulsion forces between the electrons will be very large and the atom will become unstable.

(vi) So maximum number of electrons in any outermost orbit cannot be more than 8, because of the octet rule which states maximum 8 electrons can be present in any orbit for the atom to be stable.