1. Find Arsenic's Atomic Number:
Arsenic has an atomic number of 33, meaning it has 33 protons and 33 electrons.
2. Identify the Preceding Noble Gas:
The noble gas that comes before arsenic on the periodic table is argon (Ar), which has an atomic number of 18.
3. Write the Noble Gas Core:
The noble gas configuration of argon is [Ar].
4. Determine the Remaining Electrons:
Arsenic has 33 electrons and argon has 18 electrons, leaving 15 electrons to account for (33 - 18 = 15).
5. Fill the Remaining Orbitals:
- The next orbital is the 4s orbital, which can hold 2 electrons: [Ar] 4s²
- Then, the 3d orbital is filled with 10 electrons: [Ar] 4s² 3d¹⁰
- Finally, the 4p orbital receives the remaining 3 electrons: [Ar] 4s² 3d¹⁰ 4p³
Therefore, the noble gas configuration of arsenic is [Ar] 4s² 3d¹⁰ 4p³.
