Noble Gas Configuration – Shorthand Electron Configuration


Noble Gas Configuration
The noble gas configuration is a shorthand electron configuration for atoms.

In chemistry, the noble gas configuration is a shorthand method of writing an atom’s electron configuration. The reason for using the noble gas configuration is because the full electron configuration becomes very long for atoms with high atomic numbers.

Here is a look at how to write a noble gas configuration and a list of the electron configurations for all 118 elements.

How to Write a Noble Gas Configuration

The noble gas configuration gives the noble gas core that occurs before the element on the periodic table and then the electron configuration of the atom’s valence electrons. But, you need to understand how to write the full electron configuration to find the number of valence electrons.

Here are the steps for writing a noble gas configuration:

Aufbau Principle
Applying the Aufbau principle makes writing electron configurations much simpler.
  1. Find the number of electrons for the atom. For a neutral atom, this is the same as the atomic number. (For an ion, the number of electrons is not the same as the number of protons, but otherwise the same steps apply.)

  2. Fill in the electron shells and energy levels with the electrons.

    Each s shell holds up to 2 electrons.
    Each p shell holds up to 6 electrons.
    Each d shell holds up to 10 electrons.
    Each f shell holds up to 14 electrons.

  3. Follow the Aufbau rule and write the full electron configuration. The Aufbau principle states that electrons fill lower energy levels before adding to higher energy levels. While you can use brute force to write the configuration, it’s easier to draw a diagram and follow the diagonal:

    1s
    2s 2p
    3s 3p 3d
    4s 4p 4d 4f
    5s 5p 5d 5f
    6s 6p 6d
    7s 7p
    8s

    Notice the orbits overlap, so you don’t just fill the shells sequentially (1, 2, 3, 4, …). Instead, use Madelung’s rule:

    1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7p

    Note: Madelung’s rule is not a hard-and-fast rule, especially where some of the heavier transition metals are concerned. Relativistic effects come into play and change the order.
  4. Find the noble gas preceding the element on the periodic table. Write the noble gas configuration by writing the noble gas core, followed by the valence electrons. A noble gas core is the noble gas element symbol enclosed in brackets: [He], [Ne], [Ar], [Kr], [Xe], or [Rn]. The valence electrons are “leftover” electrons that don’t fill a shell or satisfy the octet rule (except for noble gases) or 18-electron rule (transition metals). There are two easy ways to identify them. Valence electrons are the electrons leftover past the noble gas electron configuration. They are also characteristic of an element group. For example, the alkali metals always have 1 valence electron.

Noble Gas Configuration Examples

For example, write the noble gas configuration of sodium.

  • The atomic number of sodium is 11, so you know the neutral atom has 11 protons and also 11 electrons.
  • Filling in the electron shells using the Aufbau principle gives a configuration of 1s2 2s2 sp6 3s1. Add up the superscripts and double-check to make sure you have the correct number of electrons.
  • Write the noble gas configuration. Looking at a periodic table, note the noble gas before sodium is neon. The electron configuration of neon is 1s2 2s2 2p6. So, the noble gas core symbol [Ne] replaces that portion of the sodium electron configuration. The noble gas configuration for sodium is [Ne] 3s1.

For example, write the noble gas configuration of neon.

  • Neon is a noble gas, but you can do better than just write [Ne] and call it good. First, use the periodic table and see the number of electrons for a neon atom is 10.
  • Follow the Aufbau principle and fill electron shells: 1s2 2s2 2p6
  • Write the noble gas configuration using the noble gas core before neon on the periodic table, followed by the valence electrons. The noble gas configuration of neon is [He] 2s2 2p6. Notice the valence of neon is 8 (2 electrons in the 2s shell and 6 electrons in the 2p shell), which indicates it has a filled octet.

List of Noble Gas Configurations for All 118 Elements

 NUMBER ELEMENTELECTRON CONFIGURATION
1Hydrogen1s1
2Helium1s2
3Lithium[He]2s1
4Beryllium[He]2s2
5Boron[He]2s22p1
6Carbon[He]2s22p2
7Nitrogen[He]2s22p3
8Oxygen[He]2s22p4
9Fluorine[He]2s22p5
10Neon[He]2s22p6
11Sodium[Ne]3s1
12Magnesium[Ne]3s2
13Aluminum[Ne]3s23p1
14Silicon[Ne]3s23p2
15Phosphorus[Ne]3s23p3
16Sulfur[Ne]3s23p4
17Chlorine[Ne]3s23p5
18Argon[Ne]3s23p6
19Potassium[Ar]4s1
20Calcium[Ar]4s2
21Scandium[Ar]3d14s2
22Titanium[Ar]3d24s2
23Vanadium[Ar]3d34s2
24Chromium[Ar]3d54s1
25Manganese[Ar]3d54s2
26Iron[Ar]3d64s2
27Cobalt[Ar]3d74s2
28Nickel[Ar]3d84s2
29Copper[Ar]3d104s1
30Zinc[Ar]3d104s2
31Gallium[Ar]3d104s24p1
32Germanium[Ar]3d104s24p2
33Arsenic[Ar]3d104s24p3
34Selenium[Ar]3d104s24p4
35Bromine[Ar]3d104s24p5
36Krypton[Ar]3d104s24p6
37Rubidium[Kr]5s1
38Strontium[Kr]5s2
39Yttrium[Kr]4d15s2
40Zirconium[Kr]4d25s2
41Niobium[Kr]4d45s1
42Molybdenum[Kr]4d55s1
43Technetium[Kr]4d55s2
44Ruthenium[Kr]4d75s1
45Rhodium[Kr]4d85s1
46Palladium[Kr]4d10
47Silver[Kr]4d105s1
48Cadmium[Kr]4d105s2
49Indium[Kr]4d105s25p1
50Tin[Kr]4d105s25p2
51Antimony[Kr]4d105s25p3
52Tellurium[Kr]4d105s25p4
53Iodine[Kr]4d105s25p5
54Xenon[Kr]4d105s25p6
55Cesium[Xe]6s1
56Barium[Xe]6s2
57Lanthanum[Xe]5d16s2
58Cerium[Xe]4f15d16s2
59Praseodymium[Xe]4f36s2
60Neodymium[Xe]4f46s2
61Promethium[Xe]4f56s2
62Samarium[Xe]4f66s2
63Europium[Xe]4f76s2
64Gadolinium[Xe]4f75d16s2
65Terbium[Xe]4f96s2
66Dysprosium[Xe]4f106s2
67Holmium[Xe]4f116s2
68Erbium[Xe]4f126s2
69Thulium[Xe]4f136s2
70Ytterbium[Xe]4f146s2
71Lutetium[Xe]4f145d16s2
72Hafnium[Xe]4f145d26s2
73Tantalum[Xe]4f145d36s2
74Tungsten[Xe]4f145d46s2
75Rhenium[Xe]4f145d56s2
76Osmium[Xe]4f145d66s2
77Iridium[Xe]4f145d76s2
78Platinum[Xe]4f145d96s1
79Gold[Xe]4f145d106s1
80Mercury[Xe]4f145d106s2
81Thallium[Xe]4f145d106s26p1
82Lead[Xe]4f145d106s26p2
83Bismuth[Xe]4f145d106s26p3
84Polonium[Xe]4f145d106s26p4
85Astatine[Xe]4f145d106s26p5
86Radon[Xe]4f145d106s26p6
87Francium[Rn]7s1
88Radium[Rn]7s2
89Actinium[Rn]6d17s2
90Thorium[Rn]6d27s2
91Protactinium[Rn]5f26d17s2
92Uranium[Rn]5f36d17s2
93Neptunium[Rn]5f46d17s2
94Plutonium[Rn]5f67s2
95Americium[Rn]5f77s2
96Curium[Rn]5f76d17s2
97Berkelium[Rn]5f97s2
98Californium[Rn]5f107s2
99Einsteinium[Rn]5f117s2
100Fermium[Rn]5f127s2
101Mendelevium[Rn]5f137s2
102Nobelium[Rn]5f147s2
103Lawrencium[Rn]5f147s27p1
104Rutherfordium[Rn]5f146d27s2
105Dubnium*[Rn]5f146d37s2
106Seaborgium*[Rn]5f146d47s2
107Bohrium*[Rn]5f146d57s2
108Hassium*[Rn]5f146d67s2
109Meitnerium*[Rn]5f146d77s2
110Darmstadtium*[Rn]5f146d97s1
111Roentgenium*[Rn]5f146d107s1
112Copernium*[Rn]5f146d107s2
113Nihonium*[Rn]5f146d107s27p1
114Flerovium*[Rn]5f146d107s27p2
115Moscovium*[Rn]5f146d107s27p3
116Livermorium*[Rn]5f146d107s27p4
117Tennessine*[Rn]5f146d107s27p5
118Oganesson*[Rn]5f146d107s27p6
Noble gas configurations with * are predicted values.

References

  • Dzikowski, K. D.; et al. (2021). “Relativistic effective charge model of a multi-electron atom”. Journal of Physics B: Atomic, Molecular and Optical Physics 54 (11): 115002. doi:10.1088/1361-6455/abdaca
  • Langmuir, Irving (June 1919). “The Arrangement of Electrons in Atoms and Molecules”. Journal of the American Chemical Society. 41 (6): 868–934. doi:10.1021/ja02227a002
  • Rayner-Canham, Geoff; Overton, Tina (2014). Descriptive Inorganic Chemistry (6th ed.). Macmillan Education. ISBN 978-1-319-15411-0.
  • Stoner, E.C. (1924). “The distribution of electrons among atomic levels”. Philosophical Magazine. 6th Series. 48 (286): 719–36. doi:10.1080/14786442408634535
  • Wong, D. Pan (1979). “Theoretical justification of Madelung’s rule”. Journal of Chemical Education. 56 (11): 714–18. doi:10.1021/ed056p714