Orbitals and electrons in boxes
| English | Chinese | Pinyin |
|---|---|---|
| orbital | 轨道 | guǐ dào |
| spin | 自旋 | zì xuán |
| free radical | 自由基 | zì yóu jī |
| unpaired electron | 未成对电子 | wèi chéng duì diàn zi |
| repulsion | 排斥 | pái chì |
Drawing electrons in boxes
- We can draw each orbital 轨道 as a box and each electron as an arrow.
- This shows spin 自旋 and how orbitals fill.
- It also reveals free radicals 自由基 — species with unpaired electrons 未成对电子.
Each orbital can hold a maximum of two electrons, which must have opposite spins.
This is why 'electrons in boxes' show at most two arrows, pointing opposite ways.
Spin and filling rules
- Two electrons in the same orbital must point opposite ways (opposite spin).
- Within a sub-shell, electrons fill empty orbitals singly first (parallel spins) before pairing up.
- Spreading out keeps the negative electrons apart, lowering repulsion 排斥.
For nitrogen ($1\text{s}^2\,2\text{s}^2\,2\text{p}^3$): the three 2p orbitals each take one electron first.
Electrons in boxes for nitrogen: paired spins oppose; 2p fills singly with parallel spins
Filling the orbitals
Drag the proton number up and watch electrons fill the shells and sub-shells in order — 1s, 2s, 2p … — each box holding a spin-paired pair.
Two electrons sharing one orbital must:
Electrons in the same orbital have opposite spins; this is why a box holds at most two arrows pointing opposite ways.
Within a sub-shell, electrons:
Filling singly first keeps the electrons apart, reducing repulsion (e.g. nitrogen's three 2p orbitals each get one).
Orbital shapes
- an s orbital is a sphere centred on the nucleus.
- a p orbital is a dumbbell (two lobes); the three p orbitals point along the $x$, $y$ and $z$ axes.
An s orbital is a sphere; the three p orbitals are dumbbells along x, y and z
The shape of a p orbital is:
An s orbital is a sphere; each p orbital is a dumbbell, and the three point along x, y and z.
Match each term to what it means.
s is spherical, p is a dumbbell; every orbital holds 2 paired electrons, and they spread out singly first (Hund's rule).
An s orbital is spherical; a p orbital is shaped like a ______.
The three p orbitals are dumbbells pointing along the x, y and z axes.
Free radicals
- A free radical is a species with one or more unpaired electrons.
- Free radicals are very reactive.
A free radical is a species that:
Free radicals carry unpaired electrons, which makes them highly reactive.
You've got it
- paired electrons in one orbital have opposite spins; sub-shells fill singly first (parallel) then pair
- s orbital = sphere; p orbital = dumbbell along $x$, $y$, $z$
- a free radical has unpaired electrons and is very reactive