To determine the electron configuration for nobelium (No), we must understand the principles governing electron configurations and the periodic table's structure.
1. Atomic Number: Nobelium has an atomic number of 102. This means it has 102 protons and, in a neutral atom, it also has 102 electrons.
2. Filling Order of Orbitals: Electrons fill orbitals in a specific order based on increasing energy levels. The general sequence is:
- 1s, 2s, 2p,
- 3s, 3p, 4s,
- 3d, 4p, 5s,
- 4d, 5p, 6s,
- 4f, 5d, 6p, 7s,
- 5f, 6d, 7p.
3. Noble Gas Shortcut: To simplify writing the electron configuration, use the electron configuration of the nearest previous noble gas and add the required electrons to it. For nobelium, the nearest noble gas is radon (Rn), with an atomic number of 86.
4. Extended Configuration: For nobelium:
- Radon has an electron configuration of [Rn]: [tex]\(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^6\)[/tex].
5. Remaining Electrons After Radon: After accounting for the 86 electrons in radon, nobelium has 102 - 86 = 16 electrons remaining to be placed.
- The next electrons go into the 7s and 5f orbitals.
- The [tex]\(7s\)[/tex] orbital can hold 2 electrons.
- The [tex]\(5f\)[/tex] orbital can hold up to 14 electrons.
6. Final Configuration:
- Adding these remaining electrons to the configuration of radon, we have:
- [tex]\(7s^2 5f^{14}\)[/tex].
Therefore, the electron configuration for nobelium is:
[tex]\[ \mathbf{[Rn] \, 7s^2 \, 5f^{14}} \][/tex]
Hence, among the given options, the correct electron configuration for nobelium is:
[tex]\[ [Rn] 7s^2 5f^{14} \][/tex]
Thus, the answer is:
[tex]\[1\][/tex]
Therefore, the electron configuration for nobelium (No) is [Rn] 7s^2 5f^{14}, which corresponds to option 1.
