The quantum numbers are four: major (n), minor (l), magnetic (m or ml) and spin (s or mS). They have the function of locating the electrons, which is why there are no electrons that have the same four quantum numbers.
Principal Quantum Number
O principal quantum number (n) is the one that indicates the energy levels, that is, the electronic layer in which the electron is.
The electronic layers K, L, M, N, O, P and Q represent, respectively, the following main quantum numbers 1, 2, 3, 4, 5, 6 and 7:
K = 1, L = 2, M = 3, N = 4, O = 5, P = 6, Q = 7
Secondary Quantum Number
O secondary, azimuthal or angular momentum quantum number (l) is the one that indicates the energy sublevels, that is, the energy sublevel to which the electron belongs.
The energy sublevels s, p, d and f represent, respectively, the following secondary quantum numbers 0, 1, 2 and 3:
s: l = 0, p: l = 1, d: l = 2, f: l = 3
Magnetic Quantum Number
O magnetic quantum number (m or m1) is the one that indicates the orbit where the electrons meet:
- The s sublevel has 1 orbital, which is the (0) orbital.
- The p sublevel has 3 orbitals, which are the (0), (+1) and (-1) orbitals.
- The d sublevel has 5 orbitals, which are the (-2), (-1), (0), (+1) and (+2) orbitals.
- The f sublevel has 7 orbitals, which are the (-3), (-2), (-1), (0), (+1), (+2) and (+3) orbitals.
Spin Quantum Number
O spin quantum number (s or ms) is the one that indicates the direction of rotation of the electron:
If the orbital of a sublevel is negative, the rotation is in the negative direction, which is represented by an up arrow. But if the orbital of a sublevel is positive, the rotation is in the positive direction, which is represented by a downward arrow.
Representation of Quantum Numbers
Example of the Iron Element (26Faith)
Electronic iron distribution: 1s2 2s2 2p6 3s2 3p6 4s2 3d6
- Taking into account that its most energetic electron is in shell 3, then, n = 3.
- Its sublevel is d, so, l = 2.
- Sublevel d has 5 orbits. When distributing the electrons, the last one is in the -2 orbital, so, m = -2.
- The spin(s) can be +½ like -½.
What is Electronic Distribution?
THE eletronic distribution it's the way chemical elements are ordered according to their energy. It is from it that quantum numbers can locate electrons.
Read too Pauling diagram and Valencia layer.
Exercises
1. (UFPA) - The main quantum numbers "n", secondary "l", magnetic "m" of the most energetic electron of the chlorine atom are respectively:
(Data Cl: Z=17)
a) 3, 1, 0
b) 3, 1, +1
c) 2, 0, +1
d) 2, 1, -1
e) 2, 3, 0
Alternative to: 3, 1, 0
2. (UERN/2015) - The main application of bromine is the production of ethylene bromide, which is used in motor fuels, in order to avoid the accumulation of lead inside the cylinders.
Considering that the atomic number of bromine is 35, it is said to have:
I. The main quantum number equal to 4.
II. 7 complete orbitals.
III. 5 electrons at the valence level.
IV. The magnetic quantum number equal to 0.
V. 5 electrons in the last shell, with azimuthal quantum number equal to 1.
Only the statements are correct.
a) I and IV.
b) I, II and V.
c) III, IV and V.
d) I, II, IV and V.
Alternative d: I, II, IV and V.
Check entrance exam questions with a commented resolution in: Exercises on the Periodic Table.
