Understanding Electron Affinity
Electron affinity refers to the energy change that occurs when an electron is added to a neutral atom in the gas phase. Atoms with high electron affinity tend to gain electrons more readily, while those with low electron affinity are less likely to do so.
Analyzing the Options
- Nitrogen (N):
- Has a half-filled p-orbital configuration, making it relatively stable.
- Its electron affinity is negative, indicating it does not favorably accept an electron.
- Oxygen (O):
- Has a higher electron affinity than nitrogen due to its increased nuclear charge.
- Accepting an electron leads to a more stable configuration, resulting in a significant release of energy.
- Argon (Ar):
- A noble gas with a completely filled outer shell (octet).
- This stable configuration means it has very little tendency to gain an electron, resulting in a low or negligible electron affinity.
- Boron (B):
- While not as stable as nitrogen, it can accept an electron, albeit less favorably than oxygen.
- It has a positive electron affinity, indicating it can gain an electron but with less energy release than oxygen.
Conclusion: Why Argon Has the Lowest Electron Affinity
- Noble Gas Stability: Argon, being a noble gas, has a fully filled valence shell. This configuration inherently makes it very stable and not inclined to accept additional electrons.
- Comparative Analysis: Among the options given, argon has the least tendency to gain an electron, resulting in the lowest electron affinity.
Thus, the correct answer is option C: Argon.