# Electron configurations problems and solutions

1. What is the electron configuration of an oxygen atom? Solution: The electron configuration of oxygen is 1s² 2s² 2p⁴.

2. What is the electron configuration of a sodium (Na) ion (Na⁺)? Solution: The electron configuration of a sodium ion (Na⁺) is 1s² 2s² 2p⁶.
3. How many unpaired electrons are in a carbon (C) atom? Solution: Carbon has the electron configuration 1s² 2s² 2p². Therefore, it has 2 unpaired electrons.
4. What is the electron configuration of a sulfur ion (S²-)? Solution: The electron configuration of a sulfur ion (S²-) is 1s² 2s² 2p⁶ 3s² 3p⁶.
5. What element has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹? Solution: The element with this electron configuration is Potassium (K).
6. How many valence electrons does a chlorine (Cl) atom have? Solution: Chlorine has the electron configuration [Ne] 3s² 3p⁵, so it has 7 valence electrons.
7. What is the electron configuration of a calcium (Ca) ion (Ca²+)? Solution: The electron configuration of a calcium ion (Ca²+) is 1s² 2s² 2p⁶ 3s² 3p⁶.
8. What element has the electron configuration [Kr] 5s² 4d¹⁰ 5p⁶ 6s¹? Solution: The element with this electron configuration is Cesium (Cs).
9. How many valence electrons does a phosphorus (P) atom have? Solution: Phosphorus has the electron configuration [Ne] 3s² 3p³, so it has 5 valence electrons.
10. What is the electron configuration of a fluorine (F) atom? Solution: The electron configuration of fluorine is 1s² 2s² 2p⁵.
11. What is the electron configuration of a magnesium (Mg) ion (Mg²+)? Solution: The electron configuration of a magnesium ion (Mg²+) is 1s² 2s² 2p⁶.
12. What element has the electron configuration 1s² 2s² 2p⁶ 3s² 3p²? Solution: The element with this electron configuration is Silicon (Si).
13. How many unpaired electrons are in a nitrogen (N) atom? Solution: Nitrogen has the electron configuration 1s² 2s² 2p³. Therefore, it has 3 unpaired electrons.
14. What is the electron configuration of a lithium (Li) atom? Solution: The electron configuration of lithium is 1s² 2s¹.
15. How many valence electrons does an argon (Ar) atom have? Solution: Argon has the electron configuration [Ne] 3s² 3p⁶, so it has 8 valence electrons.
16. What is the electron configuration of a boron (B) atom? Solution: The electron configuration of boron is 1s² 2s² 2p¹.
17. What element has the electron configuration [Ar] 4s² 3d¹⁰ 4p²? Solution: The element with this electron configuration is Germanium (Ge).
18. What is the electron configuration of a helium (He) atom? Solution: The electron configuration of helium is 1s².
19. How many unpaired electrons are in a neon (Ne) atom? Solution: Neon has the electron configuration 1s² 2s² 2p⁶. Therefore, it has 0 unpaired electrons.
20. What element has the electron configuration [Kr] 5s² 4d¹⁰ 5p⁵? Solution: The element with this electron configuration is Iodine (I).

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