VSEPR and Bond Hybridization · VSEPR与键杂化
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| VSEPR/ˈvespə/ | 价层电子对互斥 | jià céng diàn zi duì hù chì |
| hybridization/ˌhaɪbrɪdaɪˈzeɪʃn/ | 杂化 | zá huà |
Why molecules have shapes
- Molecules are not flat blobs -- they have definite 3D shapes.
- Water is bent; carbon dioxide is a straight line.
- One simple idea predicts every shape.
- Electron pairs push apart as far as they can.
分子为何有形状
- 分子不是扁平的团块——它们有确定的三维形状。
- 水是弯的;二氧化碳是一条直线。
- 一个简单的思想就能预测所有形状。
- 电子对尽可能地相互推开。
Electron pairs spread out
- VSEPR 价层电子对互斥 says electron pairs repel and spread as far apart as possible.
- Count the groups (bonds and lone pairs) around the central atom.
- Their arrangement sets the shape.
电子对散开
- 价层电子对互斥说电子对相斥并尽可能远地散开。
- 数一数中心原子周围的基团(键和孤对电子)。
- 它们的排列决定形状。
VSEPR predicts shape by assuming electron groups... · VSEPR通过假设电子基团...来预测形状
Repelling groups spread out, which fixes the geometry. · 相互排斥的基团散开，从而确定了几何构型。
The common shapes
- 2 groups give linear ($180^\circ$); 3 groups give trigonal planar ($120^\circ$).
- 4 groups give tetrahedral ($109.5^\circ$).
- Lone pairs push harder, bending the shape -- water comes out bent.
常见形状
- 2 个基团给出直线形($180^\circ$);3 个给出平面三角形($120^\circ$)。
- 4 个给出四面体形($109.5^\circ$)。
- 孤对电子推得更用力,使形状弯折——水就是弯的。
What is the shape of $\text{CH}_4$ (4 bonds, no lone pairs)? · $\text{CH}_4$（4个键，无孤对电子）的形状是什么？
Four groups spread to a tetrahedron at $109.5^\circ$. · 四个基团在$109.5^\circ$处展开呈四面体分布。
Water ($\text{H}_2\text{O}$) has 2 bonds and 2 lone pairs. Its shape is... · 水 ($\text{H}_2\text{O}$) 有 2 个键和 2 对孤对电子。它的形状是...
The two lone pairs push the two bonds into a bent shape. · 两个孤对电子将两个键推成弯曲形状。
A central atom with exactly 2 electron groups has a ____ shape. · 恰好有2个电子基团的中心原子具有____形状。
Two groups point opposite ways, $180^\circ$ apart -- linear. · 两组方向相反，相距$180^\circ$——线性。
Hybridization matches the geometry
- Hybridization 杂化 mixes atomic orbitals to match the shape.
- 2 groups give sp; 3 groups give sp$^2$; 4 groups give sp$^3$.
- Just count the groups and read off the label.
杂化与几何形状相匹配
- 杂化把原子轨道混合以匹配形状。
- 2 个基团给出 sp;3 个给出 sp$^2$;4 个给出 sp$^3$。
- 只要数基团数目,再读出标记即可。
Predict the shape · 预测形状
Count bonding pairs and lone pairs, then read off the VSEPR shape. · 计数成键对和孤对电子，然后读出VSEPR形状。
Match the number of electron groups to the hybridization. · 将电子基团数量与杂化方式匹配。
Hybridization counts groups, so 2 = sp, 3 = sp$^2$, 4 = sp$^3$. · 杂化按基团计数，所以2 = sp，3 = sp$^2$，4 = sp$^3$。
Predict the shape of $\text{CH}_4$ and $\text{H}_2\text{O}$.
- $\text{CH}_4$: 4 bonds, no lone pairs, so tetrahedral and sp$^3$.
- $\text{H}_2\text{O}$: 2 bonds plus 2 lone pairs, so bent, still sp$^3$.
预测 $\text{CH}_4$ 和 $\text{H}_2\text{O}$ 的形状。
- $\text{CH}_4$:4 个键,无孤对电子,所以是四面体形、sp$^3$。
- $\text{H}_2\text{O}$:2 个键加 2 对孤对电子,所以是弯形,仍是 sp$^3$。
Lone pairs must be counted as electron groups when predicting shape. · 预测形状时必须将孤对电子计为电子基团。
Lone pairs occupy space and bend the geometry. · 孤对电子占据空间并使几何构型弯曲。
Count lone pairs as electron groups -- they take up space and bend the shape, even though they do not appear in the shape's name. Water is "bent," not "linear," because of its two lone pairs. Hybridization follows the number of groups, not the number of bonds alone.
把孤对电子当作电子基团来数——它们占据空间并使形状弯折,尽管它们不出现在形状的名字里。水是"弯形"而非"直线形",正是因为它的两对孤对电子。杂化跟随基团数目,而不仅仅是键的数目。
VSEPR predicts shape by spreading electron groups as far apart as possible: 2 groups linear, 3 trigonal planar, 4 tetrahedral, with lone pairs bending the result. Hybridization matches the count -- sp, sp$^2$, sp$^3$ for 2, 3, 4 groups. Always count lone pairs as groups.
价层电子对互斥通过让电子基团尽可能远地散开来预测形状:2 个基团为直线形,3 个为平面三角形,4 个为四面体形,孤对电子使结果弯折。杂化与之匹配——2、3、4 个基团分别为 sp、sp$^2$、sp$^3$。始终把孤对电子当作基团来数。