What are the electron configurations of lithium, oxygen, nitrogen, and potassium?

1 Answer
Jan 22, 2018

Lithium: 1s^2 2s^1
Oxygen: 1s^2 2s^2 2p^4
Nitrogen: 1s^2 2s^2 2p^3
Potassium: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1

Explanation:

Lithium:

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From its position, we know that it has 1 valence electron in the 2s orbital series (because it's in the second period): 2s^1.

We also know that its 1s orbital is full, because to get to lithium in the periodic table, we have to pass 1s. There are 2 electrons in an s orbital; this means that it has 2 electrons in its 1s orbital: 1s^2.

Putting it all together, we get 1s^2 2s^1.

Oxygen:

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From its position in the periodic table, we know that it has 4 valence electrons in the 2p orbital series (because it's in the second period): 2p^4.
We also know that:

  • Its 1s orbital is full. There are 2 electrons in an s orbital; this means that it has 2 electrons in its 1s orbital: 1s^2.
  • Its 2s orbital is full. There are 2 electrons in an s orbital; this means that it has 2 electrons in its 2s orbital: 2s^2.

Putting it all together, we get 1s^2 2s^2 2p^4.

Nitrogen:

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Nitrogen is directly to the left of oxygen in the periodic table. This tells us that it has one less electron than oxygen—therefore, its electron configuration is the exact same as oxygen's, except with one less electron in the valence energy level.

Oxygen's electron configuration is 1s^2 2s^2 2p^4.
After taking one electron from that, it becomes 1s^2 2s^2 2p^3—nitrogen.

Potassium:

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From its position in the periodic table, we know that it has 1 valence electron in the 4s orbital series (because it's in the s block of the fourth period): 4s^1.
We also know that:

  • Its 1s orbital is full. There are 2 electrons in an s orbital; this means that it has 2 electrons in its 1s orbital: 1s^2.

  • Its 2s orbital is full. There are 2 electrons in an s orbital; this means that it has 2 electrons in its 2s orbital: 2s^2.

  • Its 2p orbital is full. There are 6 electrons in an s orbital; this means that it has 6 electrons in its 2p orbital: 2p^6.

  • Its 3s orbital is full. There are 2 electrons in an s orbital; this means that it has 2 electrons in its 3s orbital: 3s^2.

  • Its 3p orbital is full. There are 6 electrons in an s orbital; this means that it has 6 electrons in its 3p orbital: 3p^6.

Putting it all together, we get 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1.