Noble Gas Configuration
Ck12 Science
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Printed: August 10, 2014
AUTHOR
Ck12 Science
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Chapter 1. Noble Gas Configuration
C HAPTER
1
Noble Gas Configuration
• Use the noble gas configuration approach to write electron configurations for the elements.
How does it feel to be full after a meal?
You had a great meal, but cannot put another bite in your mouth because there is no place for it to go. The noble
gases have the same problem –there is no room for any more electrons in their outer shells. They are completely full
and cannot handle any more.
Noble Gas Configurations
Sodium, element number eleven, is the first element in the third period of the periodic table. Its electron configuration
is 1s2 2s2 2p6 3s1 . The first ten electrons of the sodium atom are the inner-shell electrons and the configuration of just
those ten electrons is exactly the same as the configuration of the element neon (Z = 10). This provides the basis for a
shorthand notation for electron configurations called the noble gas configuration. The elements that are found in the
last column of the periodic table are an important group of elements that are called the noble gases. They are helium,
neon, argon, krypton, xenon, and radon. A noble gas configuration of an atom consists of the elemental symbol of
the last noble gas prior to that atom, followed by the configuration of the remaining electrons. So for sodium, we
make the substitution of [Ne] for the 1s2 2s2 2p6 part of the configuration. Sodium’s noble gas configuration becomes
[Ne]3s1 . Table 1.1 shows the noble gas configurations of the third period elements.
TABLE 1.1: Electron Configurations of Third-Period Elements
Element Name
Symbol
Atomic Number
Sodium
Na
11
Noble Gas Electron
Configuration
[Ne]3s1
1
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TABLE 1.1: (continued)
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Mg
Al
Si
P
S
Cl
Ar
12
13
14
15
16
17
18
[Ne]3s2
[Ne]3s2 3p1
[Ne]3s2 3p2
[Ne]3s2 3p3
[Ne]3s2 3p4
[Ne]3s2 3p5
[Ne]3s2 3p6
Again, the number of valence electrons increases from one to eight across the third period.
The fourth and subsequent periods follow the same pattern except for using a different noble gas. Potassium has
nineteen electrons, one more than the noble gas argon, so its configuration could be written as [Ar]4s1 . In a similar
fashion, strontium has two more electrons than the noble gas krypton, which would allow us to write its electrons
distribution as [Kr]5s2 . All the elements can be represented in this fashion.
Summary
• The noble gas configuration system allows some shortening of the total electron configuration by using the
symbol for the noble gas of the previous period as part of the pattern of electrons.
Practice
Use the link below to practice writing noble gas configurations:
http://www.sciencegeek.net/Chemistry/taters/Unit2ElectronNotations.htm
Review
Questions
1.
2.
3.
4.
What is the element represented by [Ne]3s2 3p2 ?
What element has this electron configuration [Ar]3d7 4s2 ?
What noble gas would be part of the electron configuration notation for Mn?
How would you write the electron configuration for Ba?
• noble gas configuration: Consists of the elemental symbol of the last noble gas prior to that atom, followed
by the configuration of the remaining electrons.
References
1. User:Danbold/Wikipedia. http://commons.wikimedia.org/wiki/File:Set_dinner_table.jpg .
2