Write the ground state electron configuration for: A) Fe B) Al Include also the noble gas shortcut too separately for each one.
The correct answer and explanation is:
Correct Answer:
A) Iron (Fe):
- Atomic Number: 26
- Full Electron Configuration:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶ - Noble Gas Shortcut:
[Ar] 4s² 3d⁶
B) Aluminum (Al):
- Atomic Number: 13
- Full Electron Configuration:
1s² 2s² 2p⁶ 3s² 3p¹ - Noble Gas Shortcut:
[Ne] 3s² 3p¹
Explanation (Approx. 300 words):
Electron configuration describes the distribution of electrons among the orbitals of an atom. Each element has a unique configuration based on its atomic number — the number of protons and electrons in a neutral atom.
A) Iron (Fe):
Iron has 26 electrons. The electrons fill the orbitals in order of increasing energy:
- 1s fills first with 2 electrons
- Then 2s² and 2p⁶ (completing the 2nd energy level)
- Then 3s² and 3p⁶ (completing the 3rd energy level up to p)
- Then 4s² is filled before the 3d orbitals (because 4s is lower in energy initially)
- Finally, 6 electrons go into 3d, giving 3d⁶.
Hence, the full configuration:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
Using the noble gas shortcut, [Ar] stands for the electron configuration of Argon (atomic number 18):
[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶
So Fe becomes: [Ar] 4s² 3d⁶
B) Aluminum (Al):
Aluminum has 13 electrons. Following the same filling order:
- 1s² 2s² 2p⁶ (first 10 electrons)
- Then 3s² (next 2 electrons)
- Then 3p¹ (last electron)
So, the full configuration is:
1s² 2s² 2p⁶ 3s² 3p¹
The noble gas neon (Ne) has the configuration:
[Ne] = 1s² 2s² 2p⁶
Therefore, the shortcut for Al is: [Ne] 3s² 3p¹
Using noble gas shorthand helps simplify configurations, especially for heavier elements, making it easier to identify valence electrons involved in bonding and chemical reactions.