QUANTUM
NUMBERS
Unit 4 – Y10
STARTER
To define each electron we need to give four different “data”. These data are called quantum numbers
Quantum number – n ■ n = Describes the main energy level in which the electron is found.
■ An electron in the 1st energy level --> n = 1
■ An electron in the 2nd energy level --> n = 2
■ An electron in the 3rd energy level --> n = 3 …..
What is the energy level of the electron in a circle?
1s22s22p63s1
Quantum
number – l ■ This describes the shape of
the orbital.
■ s-orbital --> l = 0
■ p-orbital --> l = 1
■ d-orbital --> l = 2
■ f-orbital --> l = 3
l
What is the quantum number of the electron in a circle?
1s22s22p63s1
Quantum number – m ■ This describes which specific
orbital the electron is in.
■ As there is only 1 type of s-orbital ->m=0
■ There are 3 types of p-orbital so we
name the middle one m = 0. Either
side we subtract 1 to give m = -1 or
add 1 to give m = 1.
■ We follow this pattern no matter
how many obitals there are.
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SUMMARY
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Write the set of quantum numbers for the
outer electron in H and Na.
Hydrogen: 1s1
n=1 , l=0, m=0, s=+1/2
Sodium: 1s22s22p63s1
n=3, l=0, m=0, s=1/2
Write the quantum numbers for each outer
electron in carbon and vanadium.
■ Carbon: electron config. 1s22s22p2
outer electrons are the 2 electrons of the higher energy level
-1
0
2p2: n=2, l=1, m=-1, s=1/2
n=2, l=1, m=0, s=1/2
1
■ Vanadium: electron config. [Ar]4s23d3
-2
-1
0
1
2
3d3: n=3, l=2, m=-2, s=1/2
n=3, l=2, m=-1, s=1/2
n=3, l=2, m=0, s=1/2
Write one possible set of quantum numbers
for an electron in a 3d orbital? A 4s orbital?
■ Electron in a 3d orbital:
-2
-1
0
■ Electron in a 4s
0
1
2
In which orbital is an electron with the
quantum numbers n = 4, l = 1, m = -1, s =
+1/2?
n = 4, l = 1, m = -1, s = +1/2
4
p
-1
0
1