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Polar Covalent Bonds 极性共价键

So far we have seen that atoms combine in two different ways. So far迄今为止，就此范围（或程度）说来 迄今为止，我们看到了两种不同的原子结合方式。

Some that are quite different in electron structure (from the opposite ends of the periodic table) react by the complete transfer of one or more electrons from one atom to another (ionic bond formation).

from the opposite ends of the periodic table周期表相对的两端 句子结构：some??react by?? Transfer 名词

那些原子结构截然不同（周期表左右两端）的原子，一个将一个或数个电子由一个原子完全传递到另一个原子的方式反应（离子键形成）。

Atoms that are identical combine by sharing one or more pairs of electrons (covalent bond formation).

相同的原子通过共用一对或多对电子（共价键形成）而结合。 Now let us look at some “in-betweeners”. 现在让我们看一下“居于中间者”。

Hydrogen and chlorine react to form a colorless, toxic gas called hydrogen chloride.

hydrogen chloride 氯化氢

氢与氯反应生成一种无色、有毒的气体氯化氢。 This reaction can be represented schematically by 这个反应可由下式表示： H ＋ Cl → HCl 或（H－Cl）

Both the hydrogen atom and the chlorine atom want an electron, so they compromise by sharing and form a covalent bond. 氢原子和氯原子都想得到一个电子，所以它们通过共用电子对结合并形成共价键。

Since the substances hydrogen and chlorine actually consist of diatomic molecules rather than single atoms, the reaction is more accurately represented by the scheme. diatomic molecules 二原子分子

由于氢和氯实际上是二原子分子而不是单个原子，反应写成下式更准确

H：H＋....：：Cl..Cl..：..2H：Cl..：

This can be more simply written as 简写为H2 ＋ Cl2 → 2HCl

One might reasonably ask why the hydrogen molecule and the chlorine molecule react at all.

有人也许会问为什么氢分子和氯分子能够完全反应。 Have we not just explained that they themselves were formed

provide a more stable arrangement of electrons? 宾语

我们不是已经解释了它们本身形成了相对稳定的电子排布了吗？

Yes, indeed, we say that. But there is stable and there is more stable.

是的，我们说过这些，但这有稳定和更稳定。

The chlorine molecule represents a more stable arrangement than separate chlorine atoms, but, given the opportunity, a chlorine atom would rather bond to hydrogen than（bond）to another chlorine atom. would rather……than含有选择得意思，“宁可……而不……” would rather与than后面为平行结构

氯分子代表着比单独的氯原子更稳定的排列，但是，若有机会，氯原子宁可与氢成键而不愿与另一个氯成键。

In a molecule of hydrogen chloride, a chlorine atom shares a pair of electrons with a hydrogen atom.

在氯化氢分子中，氯原子和氢原子共用一对电子。

In this case, and in others we shall consider, sharing does not mean sharing equally.

在这种情况下，以及我们能想到的其他情况，共用并不意味着完全分享。

Some atoms within molecules attract electrons more strongly than do other atoms.

分子中一些原子吸引电子的能力比其他原子强。

The term electronegativity is used to describe the affinity of an element in a molecule for electrons.

电负性是用来描述分子中原子的亲和力的。

The higher the electronegativity, the more strongly the atoms of an element attract electrons to themselves. 电负性越大，原子吸引电子的能力越强。

The most electronegativity element is fluorine, which is located in the upper right corner of the periodic table.

电负性最大的元素是氟，它处于元素周期表的右上角。 The electronegativity of elements decreases as one moves away from fluorine in the periodic table.

在周期表中，离氟越远，元素的电负性越弱。

Thus electronegativity decreases as one moves down a group (column) or left across a period (row). down a group (column) 由族（列）向下 left across a period (row) 由周期（行）向左

所以，由族（列）向下或由周期（行）向左，电负性减弱。

I. Comprehension

1. What is the main idea of the paragraph? A

A. There are so many kinds of chemical bonds. B. How does the ionic bond come into being. C. The noble gases are stable.

D. Can sodium atoms and chlorine atoms react with each other to form a stable arrangement of electrons.

2. What is the author’s meaning by saying “even atoms have their own standards of beauty”? B A. Atoms can detect whether an electron arrangement is beautiful or not.

B. There are standards or rules that can determine if an electron arrangement is favored or not.

C. Atoms are more favored a beautiful electron arrangement than an ugly one.

D. We can beautify atoms by their standards.

3. What’s “the standards of beauty” of atoms? C A. An octet (eight outer electrons). B. A duet (two outer electrons). C. A and B.

D. There is no such standards.

4. Are the sodium ion (Na+) and the neon atom (Ne) identical?