Sigma and pi bonds · σ 键与 π 键
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| sigma/ˈsɪɡmə/ | σ键 | σ jiàn |
| pi/paɪ/ | π键 | π jiàn |
| bond length/bɒnd leŋθ/ | 键长 | jiàn zhǎng |
| hybridisation/ˌhaɪbrɪdaɪˈzeɪʃn/ | 杂化 | zá huà |
| bond energy/bɒnd ˈenədʒi/ | 键能 | jiàn néng |
Two ways to overlap
- Covalent bonds form when orbitals overlap.
- The way they overlap gives a sigma σ键 or a pi π键 bond.
- Bond strength links to bond length 键长.
两种重叠方式
- 共价键在 轨道重叠 时形成。
- 它们重叠的方式给出 σ(sigma) 键或 π(pi) 键。
- 键的强度与键长有关。
A pi bond is formed by the sideways overlap of p orbitals. · 一个 π 键由 p 轨道的侧向重叠形成。
Sigma bonds form by end-on overlap. · σ 键由端对端重叠形成。
Two kinds of overlap
- a sigma (σ) bond forms by head-on overlap between the two atoms.
- a pi (π) bond forms by the sideways overlap of two p orbitals (above and below).
- single = 1σ; double = 1σ + 1π; triple = 1σ + 2π.
两种重叠
- σ(sigma) 键由两个原子之间的 头对头 重叠形成。
- π(pi) 键由两个 p 轨道的 侧向 重叠形成(在上方和下方)。
- 单 = 1σ;双 = 1σ + 1π;三 = 1σ + 2π。
Single, double and the shared pairs · 单键、双键与共享电子对
A single bond is one shared pair (a σ bond); switch to O₂ to see a double bond — a σ plus a second shared pair, the π bond. · 一个单键是一对共享电子(一个 σ 键);切换到 O₂ 看双键——一个 σ 加上第二对共享电子,即 π 键。
A pi (π) bond forms by: · 一个 π 键由以下方式形成:
A σ bond is head-on overlap; a π bond is the sideways overlap of p orbitals. · σ 键是头对头重叠;π 键是 p 轨道的侧向重叠。
A double bond consists of: · 一个双键由以下构成:
A single bond is 1σ; a double is 1σ + 1π; a triple is 1σ + 2π. · 单键是 1σ;双键是 1σ + 1π;三键是 1σ + 2π。
Match each bond/overlap to what it is. · 把每种键/重叠与它是什么配对。
A single bond is one σ; a double bond is a σ plus a π (sideways p-orbital overlap). · 单键是一个 σ;双键是一个 σ 加一个 π(p 轨道侧面重叠)。
Hybridisation 杂化
- Hybridisation mixes orbitals in a shell into new, equal ones:
- sp → 2 orbitals (linear),
- sp² → 3 orbitals (flat, e.g. $\text{C}_2\text{H}_4$),
- sp³ → 4 orbitals (e.g. $\text{CH}_4$).
杂化
- 杂化(hybridisation) 把一个壳层中的轨道混合成新的、相等的轨道:
- sp → 2 个轨道(直线形),
- sp² → 3 个轨道(平面,例如 $\text{C}_2\text{H}_4$),
- sp³ → 4 个轨道(例如 $\text{CH}_4$)。
Methane (CH₄) uses which hybridisation? · 甲烷(CH₄)用哪种杂化?
CH₄ is tetrahedral with four equal bonds, from sp³ hybridisation. · CH₄ 是四面体形,有四个相等的键,来自 sp³ 杂化。
Bond energy 键能 and length
- bond energy = energy to break one mole of a bond (gas state).
- bond length = distance between the two bonded nuclei.
- A shorter bond is usually stronger: triple > double > single.
键能和键长
- 键能(bond energy) = 断开一摩尔键所需的能量(气态)。
- 键长(bond length) = 两个成键原子核之间的距离。
- 更短 的键通常 更强:三键 > 双键 > 单键。
Which bond is the shortest and strongest? · 哪个键最短最强?
Shorter bonds are stronger: triple > double > single in both strength and shortness. · 更短的键更强:三键 > 双键 > 单键,在强度和短度上都是。
You've got it
- σ = head-on overlap; π = sideways p-orbital overlap
- single = 1σ; double = 1σ + 1π; triple = 1σ + 2π
- hybridisation: sp (linear), sp² (flat), sp³ (tetrahedral)
- shorter bond → stronger (triple > double > single)
你掌握了
- σ = 头对头重叠;π = 侧向 p 轨道重叠
- 单 = 1σ;双 = 1σ + 1π;三 = 1σ + 2π
- 杂化:sp(直线形)、sp²(平面)、sp³(四面体形)
- 更短的键 → 更强(三键 > 双键 > 单键)