Atomic Orbitals and Aufbau

Also called

atomic orbitals · orbital shapes · s orbital · p orbital · d orbital · dumbbell orbital · Aufbau principle · Pauli exclusion principle · Hund's rule · electronic configuration · energy level diagram · 4s before 3d · chromium configuration · copper exception · quantum numbers · spin up spin down · परमाणु कक्षक · ऑफबाऊ नियम · इलेक्ट्रॉनिक विन्यास

Topics

• An orbital is the region round the nucleus where an electron is most likely to be found; it is not a fixed path.
• An s orbital is a sphere; every shell has one, and 2s is simply larger and higher in energy than 1s.
• A p orbital is a dumbbell of two lobes; from n = 2 there are three, along the x, y and z axes.
• A d orbital has four lobes like a cloverleaf (dz² has two lobes and a ring); there are five from n = 3.
• Aufbau: electrons fill from the lowest energy up: 1s 2s 2p 3s 3p 4s 3d 4p (the n + l rule puts 4s below 3d).
• Pauli: an orbital holds at most two electrons, and the two must have opposite spins (↑↓).
• Hund: in orbitals of equal energy, electrons stay single with parallel spins before any orbital gets a pair.
• Oxygen is 1s² 2s² 2p⁴: three single 2p electrons first, then the fourth pairs up.
• Chromium is 3d⁵ 4s¹ and copper 3d¹⁰ 4s¹: a half-filled or full d sub-shell is extra stable…

About this model

A GLB file of about 420 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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