Unit 1 - Lesson 03: Representing Electron Configurations using Orbital Diagrams and Quantum Numbers

Oct 26, 2026

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Unit 1, Lesson 03 explains how to represent electron configurations using orbital diagrams and quantum numbers. It describes orbital diagrams as a visualization of electron locations and spins within sub-levels, matching the information in electron configurations. It then introduces quantum numbers as an address for an electron’s position and motion, detailing principal number n, angular momentum l, magnetic quantum number ml, and spin quantum number ms, including allowed values and meaning.

LanguageEnglish

CategoryExam

FormatPDF

Pages2

Reading Time5 min

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Orbital Diagrams

Quantum Numbers

Principal Quantum Number (n)

Orbital Shape Quantum Number (l)

Magnetic Quantum Number (ml)

Magnetic Spin Quantum Number (ms)

Unit 1, Lesson 03: Representing Electron Configurations using Orbital Diagrams and Quantum Numbers A. Orbital Diagrams Sometimes it is helpful to use orbital diagrams to help visualize where the electrons are found in an atom. Orbital diagrams include the same information as the electron configuration, but they also show the electrons’ locations and spins in the sub-levels. 25Mn or | | | | | | | | | | | | | | | | | | | | | | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | 1s 2s 2px 2py 2pz 3s 3px 3py 3pz 4s 3dyz 3dxz 3dxy 3dz2 3dx2-y2 4px 4py 4pz 5s B. Quantum Numbers Another method of describing the energy and location of an electron is “quantum numbers”, which substitutes a numerical value for the letters in the electron configuration. Quantum numbers work like an address to tell us where an electron is in the space around the nucleus, and how it is moving. Each electron in an atom has a unique set of four quantum numbers. 1. The principal quantum number (n): indicates the distance that the electron is from the nucleus (which indicates the energy of the electron); the same as when writing electron configurations • the allowed values for n are 1, 2, 3 4 2. The orbital shape (or angular momentum) quantum number (l): substitutes a number for the letter that indicates the orbital’s shape • the allowed values for l are 0, 1, 2, 3 (n – 1) s is represented by l = 0 p is represented by l = 1 d is represented by l = 2 f is represented by l = 3 3. The magnetic quantum number (ml ): indicates the orientation of the orbital in 3-D space • the allowed values for ml are – l + l s is represented by ml = 0 px is represented by ml = –1 px is represented by ml = 0 px is represented by ml = +1 3dyz is represented by ml = –2 3dxz is represented by ml = –1 3dxy is represented by ml = 0 3dz2 is represented by ml = +1 3dx2-y2 is represented by ml = +1 4. The magnetic spin quantum number (ms ) indicates the spin on the electron: ms = + ½ indicates an electron spinning “up” ↑ ms = – ½ indicates an electron spinning “down” ↓ | Description | Electron Configuration Notation | Quantum Number Notation | | --- | --- | --- | | 1. The Principal Quantum Number (n):
• this is the same for both electron configurations and quantum numbers
• indicates how far the electron is from the nucleus
• the higher the number, the greater the potential energy of the electron
• the allowed values for n are 1, 2, 3 4 | n = 1, 2, 3, 4 …4 | n = 1, 2, 3, 4 …4 | | 2. The Orbital Shape or Angular Momentum Quantum Number (l):
• uses a number to represent the energy sub-levels (types of orbitals) within each principal quantum level
• indicates the shape that the electron wi moving in
• the allowed values for l are 0, 1, 2, 3 (n – 1) | s, p, d, f , g …
y | l = 0, indicates an “s” orbitall = 1, indicates a “p” orbital
l = 2, indicates a “d” orbital
l = 3 , indicates a “f” orbital | | 3. The Magnetic Quantum Number (ml):
• indicates the three dimensional orientation of an electron (which planethe electron is found in)
• the allowed values for ml are – l + l | s | ml= 0 | | | px, py, and pz z x | ml= -1 means px
ml= 0 means py
ml= +1 means pz | | | dyz, dxz, dxy, dz2, and dx2-y2
| ml= -2 means dyz
ml= -1 means dxz
ml= 0 means dxy
ml= +1 means dz2
ml= +2 means dx2-y2 | | 4. The Magnetic Spin Quantum Number (ms):
• each orbital can hold a maximum of two electrons with opposite spin (the Pauli Exclusion Principle)
• allowed values for ms are – ½ or + ½ | up (↑)
down (↓) | + ½ means an electron with an “up” spin,
– ½ means an electron with a“down” spin | Summary:

FAQs

What information do orbital diagrams show compared with electron configurations?

Orbital diagrams show where electrons are located in sub-levels and include the electrons’ spins, while still conveying the same overall information as electron configurations.

How does the principal quantum number (n) relate to an electron’s energy and distance?

The principal quantum number n indicates the electron’s distance from the nucleus, which corresponds to the electron’s energy. Allowed values are 1, 2, 3, and 4 (as given).

What do the magnetic quantum number (ml) and magnetic spin quantum number (ms) describe?

The magnetic quantum number ml gives the orbital’s 3-D orientation, while the magnetic spin quantum number ms indicates whether the electron spin is “up” (+1/2) or “down” (-1/2).

Oct 26, 2026

Upload by noah