Question

Which of the following quantum number combinations is not allowed in an atom?

A. n = 2, l = 1, mr = -1

B. n = 1, l = 1, m = 0

C. n = 8, l = 5, m = -4

D. n = 6, l = 3, m = 2

Answer 1

B. n = 1, l = 1, m = 0

Step-by-step explanation:

The quantum numbers have the function to locate an electron, so two electrons can't have all the same quantum numbers. There are four:

n - Is the principal quantum number and represents the levels. It varies from 1 to 7, and can be represented by the letters K, L, M, N, O, P, and Q;

l - Is the azimuthal quantum number and represents the sublevels. It varies from 0 to n-1, and can be represented by the letters s, p, d, e, f, g, etc.;

m - Is the magnetic quantum number and represents the orbital. It varies from -l to +l passing by the 0;

ms - Is the spin number, which represents the spin of an electron. It can be +1/2 or -1/2.

In letter B, for n=1, the maximum valor from l is n-1 = 1-1 = 0, then, l = 1 is not possible.

Answer 2

The correct answer in this question is option B. The combinations n = 1, l = 1, m = 0 is not allowed in an atom. One of the rules in quantum number combinations is that the angular quantum number (l) can be any integer from 0 to n-1. In option B, the principal quantum number (n) is equal to the angular quantum number.