Chemistry · D and f Block Elements
Work through this past-paper style MCQ, then read the full explanation. Practice more chemistry questions on mMCQ with adaptive practice and topic analytics.
Which of the following species has the maximum number of unpaired electrons?
- A
O2
- B
O+2
- C
O-2
- D
O2-2
O2 has 2 unpaired electrons, O+2 has no unpaired electrons, O-2 has paired electrons while O2-2 also has no unpaired electrons hence the correct option is A
The number of unpaired electrons in an atom or ion can be determined by examining its electron configuration. Let's analyze the given species:
1. **O2**: Molecular oxygen (O2) has a total of 16 electrons (8 electrons per oxygen atom). Its electron configuration is 1s² 2s² 2p⁴. There are two unpaired electrons in the 2p orbital.
2. **O+2**: Oxygen cation (O+2) is formed by losing two electrons from O2. Its electron configuration becomes 1s² 2s² 2p³. There is one unpaired electron in the 2p orbital.
3. **O-2**: Oxygen anion (O-2) is formed by gaining two electrons by O2. Its electron configuration becomes 1s² 2s² 2p⁶. There are no unpaired electrons.
4. **O2-2**: This is a hypothetical species, as it would mean adding two more electrons to O-2, which is not energetically favorable. If you meant O-2, please refer to the explanation for O-2 above.
Based on the analysis, **O2** has the maximum number of unpaired electrons with **two unpaired electrons**.
Molecular oxygen (O2) has a total of 16 electrons (8 electrons per oxygen atom). Its electron configuration is 1s² 2s² 2p⁴. There are two unpaired electrons in the 2p orbital.
O2 has 16 electrons having 2 unpaired electrons in a 3p orbital.
[Ne] 3s² 3p⁴
Oxygen cation (O+2) is formed by losing two electrons from O2. Its electron configuration becomes 1s² 2s² 2p³. There is one unpaired electron in the 2p orbital.
O+2 has 6 electrons and no unpaired electrons.
[He] 2s2 2p2
Oxygen anion (O-2) is formed by gaining two electrons by O2. Its electron configuration becomes 1s² 2s² 2p⁶. There are no unpaired electrons.
It has 10 electrons and all the electrons are paired
[He]2s²2p⁶
This is a hypothetical species, as it would mean adding two more electrons to O-2, which is not energetically favorable. If you meant O-2, please refer to the explanation for O-2 above.
O2-2 has 14 electrons and no unpaired electrons
[Ne] 3s² 3p²
Tagged under Chemistry · D and f Block Elements · 2019