Answer:
- C, Te, and Si have two unpaired electrons in the ground state.
Explanation:
You must draw the electron configuration.
C (carbon)
- Atomic number (Z): 12
- Number of electrons: 12
- Electron configuration of ground state, following Aufbau rules (filling orbitals in order of increasing energy):
1s² 2s² 2p²
- Electron pairing following Hund's rules (fill different orbitals of same energy, with same spin, before adding a second electron, with opposite spin, to an orgital).
1s² 2s² 2px↑ 2py↑
- As you see, these configuration shows two unpaired electrons (same spin) in the ground state.
Te (tellurium)
- Z = 52
- Number of electrons: 52
- Aufbau's rule and short notation: [Kr] 5s² 4d¹⁰ 5p⁴
- Hund's rule: [Kr] 5s² 4d¹⁰ 5px↑↓ 5py↑ 5pz↑
- This configuration shows two unpaired elecctrons (same spin).
Hf (hafnium)
- Z = 72
- Number of electrons: 72
- Aufbau's rule and short notation: [Xe] 4f¹⁴ 5d²6s²
- This configuration shows that there are not unpaired electrons (the las orbital 6s is complete with 2 electrons)
Si (silicon)
- Z = 14
- Number of electrons: 14
- Aufbau's rule and short notation: [Ne] 3s² 3p²
- Hund's rule: [Ne] 3s² 3px↑ 3py↑
- This configuration shows two unpaired electrons.
Conclusion: C, Te and Si, have two unpaired electrons (same spin) in the ground state.
