Question

which is the noble-gas notation for lead (pb)?
○ rn6s²4f¹⁴5d¹⁰6p²
○ rn6s²5d¹⁰6p²
○ xe6s²4f¹⁴5d¹⁰6p²
○ xe6s²5d¹⁰6p²

Explanation:

1. First, determine the atomic number of lead (Pb): Lead has an atomic number of 82.
2. Identify the noble gas before lead: Xenon (Xe) has an atomic number of 54, which is the noble gas with the highest atomic number less than 82.
3. Calculate the electrons to account for after Xe: $82 - 54 = 28$ electrons.
4. Fill the orbitals in order: After Xe ($[Kr]4d^{10}5s^25p^6$ or $[Xe]$ for simplicity), the next orbitals are filled as follows:

• $6s^2$ (2 electrons),
• $4f^{14}$ (14 electrons, since f - orbitals can hold 14 electrons),
• $5d^{10}$ (10 electrons, d - orbitals hold 10),
• $6p^2$ (2 electrons, p - orbitals start filling here).
• Summing these: $2 + 14 + 10 + 2 = 28$, which matches the remaining electrons.
• Radon (Rn) has an atomic number of 86, which is higher than 82, so it cannot be the noble gas core here. Also, the $4f^{14}$ subshell must be included for elements after lanthanum (atomic number 57), and lead is in that range, so the correct noble - gas notation includes the $4f^{14}$ subshell.

Answer:

[Xe]$\boldsymbol{6s^2 4f^{14} 5d^{10} 6p^2}$ (the third option: [Xe]$\boldsymbol{6s^2 4f^{14} 5d^{10} 6p^2}$)