Chapter 9 · Electrons in Atoms and the Periodic Table
9.5The Quantum-Mechanical Model: Atoms with Orbitals
10 min · two checks
Predict
What does an orbital represent?
The idea
- Define an orbital as a probability region.
- Name the information the quantum numbers organize.
The quantum-mechanical model does not give the electron a trajectory. It gives a wavefunction. The square of that function is a probability map. An orbital is one allowed map, with a characteristic energy and shape. Dots crowded near the nucleus in an s orbital do not mean the electron lives only there; they mean you are more likely to find it there.
Orbitals come in shells (the principal level n = 1, 2, 3…) and subshells (s, p, d, f). An s subshell has 1 orbital, p has 3, d has 5, f has 7. Each orbital holds at most two electrons. You do not need the full machinery of quantum numbers to write configurations, but you do need this capacity table, because it is why the periodic table has 2, 6, 10, and 14 columns in its blocks.
Keep these
- An orbital is a probability region with a definite energy.
- s, p, d, f hold 1, 3, 5, 7 orbitals.
- Two electrons per orbital, at most.