What is Atomic Orbital Theory?
Atomic orbital theory models electrons not as fixed orbits but as probability clouds around the nucleus. Each orbital is defined by quantum numbers (n, l, m_l, m_s) and can hold a maximum of 2 electrons.
An orbital is a region of space where an electron has a 90% probability of being found. Orbitals have shapes (spherical s, dumbbell-shaped p, cloverleaf d) and come in subshells (s, p, d, f).
- •Spherical shape
- •l = 0
- •1 orbital per subshell
- •Max 2 electrons
- •Example: 1s
- •Dumbbell-shaped
- •l = 1
- •3 orbitals per subshell
- •Max 6 electrons
- •Example: 2p
Step-by-step worked examples
How many electrons can fill the 2p subshell?
2p means n=2, l=1 (p orbital). There are 3 p orbitals (ml = −1, 0, +1). Each orbital holds max 2 electrons. Total: 3 × 2 = 6 electrons in 2p.
Write the quantum numbers for one electron in a 3d orbital.
3d means n=3, l=2 (d orbital). There are 5 d orbitals (ml = −2, −1, 0, +1, +2). One possible set: (n=3, l=2, ml=+1, ms=+1/2) for an electron in one 3d orbital.
Compare the size of 1s and 2s orbitals.
n=1: 1s orbital is closest to nucleus (smallest). n=2: 2s orbital is farther away (larger). Orbitals expand as n increases; higher energy.
Flashcards
Quick quiz
Q1.The shape of an s orbital is…
Q2.How many d orbitals are in a d subshell?
Q3.Which orbital is larger: 1s or 3s?
Q4.The Pauli exclusion principle states that…
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Common mistakes
Orbits and orbitals mean the same thing. — Correct: Orbits are fixed paths (Bohr model, wrong for atoms); orbitals are probability clouds (quantum model, correct).
All orbitals have the same energy. — Correct: Orbital energy increases with n (1s < 2s < 2p, etc.).
An orbital can hold any number of electrons. — Correct: Each orbital holds a maximum of 2 electrons (Pauli exclusion principle).
The 2p subshell has 1 orbital. — Correct: The 2p subshell has 3 orbitals (ml = −1, 0, +1), each holding up to 2 electrons.
FAQ
What is the atomic orbital theory definition?
Electrons exist as probability clouds (orbitals) in quantum states (n, l, ml, ms), not fixed orbits. Each orbital can hold max 2 electrons.
What are the four quantum numbers?
n (principal, energy level 1,2,3...); l (orbital shape: s,p,d,f); ml (orientation); ms (spin: ±1/2).
How many electrons can the f orbitals hold?
f subshell has l=3, ml = −3 to +3 → 7 orbitals → 14 electrons max.
Why is orbital shape important?
Shape determines how electrons interact in bonding, affecting molecular structure and chemistry.