Noble Gas Core Definition

close up of sodium on periodic table

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A noble gas core is an abbreviation in an atom's electron configuration where the previous noble gas's electron configuration is replaced with the noble gas's element symbol in brackets. Writing an electron configuration using the noble gas core can save you a lot of time!

Examples

Sodium has an electron configuration of:

1s 22s 2p 63s 1

The previous noble gas on the periodic table is neon with an electron configuration of:

1s 22s 2p 6

If this configuration is replaced by [Ne] in sodium's electron configuration it becomes:

[Ne]3s 1

This is the noble gas core notation of sodium.

With a more complex configuration, the noble gas core becomes even more helpful. Iodine (I) has a standard electron configuration of:

1s 22s 22p 63s 23p 64s 23d 104p 65s 24d 105p 5

The noble gas prior to iodine on the periodic table is krypton (Kr), which has the electron configuration:

1s 22s 22p 63s 23p 64s 23d 104p 6

This is the noble gas core for iodine, so the shorthand notation for its electron configuration becomes:

[Kr]5s 24d 105p 5
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Your Citation
Helmenstine, Anne Marie, Ph.D. "Noble Gas Core Definition." ThoughtCo, Feb. 16, 2021, thoughtco.com/definition-of-noble-gas-core-605411. Helmenstine, Anne Marie, Ph.D. (2021, February 16). Noble Gas Core Definition. Retrieved from https://www.thoughtco.com/definition-of-noble-gas-core-605411 Helmenstine, Anne Marie, Ph.D. "Noble Gas Core Definition." ThoughtCo. https://www.thoughtco.com/definition-of-noble-gas-core-605411 (accessed April 11, 2021).