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HONORS CHEMISTRY – UNIT 4
QUANTUM NUMBERS NOTES
Analogy: Imagine the propeller of an airplane. They can be certain of its position as long as it is not moving. But as the propeller begins to move, it seems to
take a different shape – that of a disk – and it position at any one instant is less certain. Electrons are much smaller and move much more quickly, creating even
greater uncertainty. Like the propeller taking the shape of a disk, the electron is no longer considered to be at a single point in space, but rather it is thought of
as a cloud. The mathematical solution established the different possible regions in space (orbitals) that electrons could occupy. These regions are summarized
using quantum numbers.
Quantum numbers - Each electron in an atom is described by four different quantum numbers. The first three (n, l, ml) specify the particular
orbital of interest, and the fourth (ms) specifies the spin of the electron within that orbital. An atomic orbital describes a 3D region of space in which
there is a high probability of finding the electron
Quantum Number
Describes
Possible Values
#1 - Principle (n)
Indicates the energy level occupied by an
electron. This tells you the relative distance
from the nucleus.
n = 1 to 7
#2 - Azimuthal (l)
Indicates the 3-dimensional shape of the
region that an electron is likely to be found.
(tells you the sublevel)
0 = s (spherical)
1 = p (dumbbell)
2 = d (fan blade/cloverleaf)
3 = f (too complex)
#3 - Magnetic (ml)
Indicates the specific orbital that an electron
is likely to be found.
(-l to +l)
#4 - Spin (ms)
Indicates the spin direction of an electron
within the orbital
+1/2 = (arrow up)
-1/2 = (arrow down)
SUBLEVELS AND ORBITALS