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called a covenlent bond.

分子是通过共用电子对将两个分离的原子结合在一起。通过共用电子对形成的键称为共价键。

A chlorine atom will pick up an extra electron from anything willing to give one up.

氯原子可以从任何愿意失去一个电子的原子处得到一个电子。

But, again, what if the only thing around is another chlorine atom?

但是，如果周围只有另一个氯原子又会怎样？

Chlorine atoms, too, can attain a more stable arrangement by sharing a pair of electrons.

氯原子同样也是通过共用电子对达到稳定结构。

Each chlorine atom in the chlorine molecule counts eight electrons around itself and concludes that it has an arrangement like that of the noble gas argon.

that it has an arrangement like that of the noble gas argon.宾语从句

氯分子中每个氯原子周围都有8个电子，并且可以断定它具有惰性气体氩一样的排布。

The shared pair of electrons in the chlorine molecule also creates a covalent bond.

氯分子中共用的一对电子同样形成共价键。

For simplicity, the hydrogen molecule is often represented as H2 and the chlorine molecule as Cl2.

the chlorine molecule as Cl2：the chlorine molecule is often represented as Cl2

为了简化，氢分子常写成H2，氯分子常写成Cl2。 The subscripts indicate two atoms per molecule. 这个下标表示每个分子中有2个原子。

In each case, the covalent bond between the atoms is understood. Sometimes the covalent bond is indicated by a dash, H-H and Cl-Cl. 在每种情况下，原子之间的共价键都可以理解，有时共价键也用一个短线表示H－H和Cl－Cl。：

Let us be sure we understand the meaning of numbers in formulas.

让我们确信我们理解公式中数字的意义。

Take a moment to establish in your mind the difference among the following: H，H2，2H，2 H2，H2O，2 H2O.

花点时间来搞清楚下面数字的不同：H，H2，2H，2 H2，H2O，2 H2O。

Is it clear to you that although H represents a single atom of hydrogen, H2 implies two atoms of H bonded together, whereas 2H represents two separate, free, and independent atoms of H?

That引导实际主语

你是否明白H代表分离的氢原子，H2代表两个H结合而成的氢分子，而2H代表分离的、自由的、孤立的氢原子吗？ On the other hand, the meaning of H2 in H2O is totally different from that of H2 as a molecule.

另一方面， H2在H2O中的意思与作为一种分子的H2完全不同。 In H2O it means that two atoms of H are individually attached to O（not to themselves!） to form a molecule of water.

在 H2O中表示两个H分别吸引O（而不是它们自己！）来形成一个水分子。

Finally, 2 H2O simply refers to two individual molecules of water.

最后，2 H2O代表两个独立的水分子。

Covalent bonds are not limited to the sharing of one pair of electrons. Consider, for example, the nitrogen atom. Its electron-dot

...N.symbol is：.

共价键不限于分享一对电子。例如，对于氮原子。它的电子

...N.式是：.

Now, after all we have learned about the octet rule we know that this electron arrangement is not complete. octet rule八耦体规则

现在，我们学习了八耦体规则。我们知道这个电子排布是不饱和的。

It has only five electrons in its outermost energy level. outermost energy level外层电子能级 在它的外层电子能级上只有5个电子。

It could shared a pair of electrons with another nitrogen atom and

..：N：N：. would then look like this：.它可以与另一个氮原子共用一对电子而变成如下形式：

..：N：N：.. The situation has not improved a great deal. 情况并没有发生太大变化。

Each nitrogen atom in this arrangement has only six electrons surrouding it (not eight).

每个氮原子周围电子排布只有6个电子（不是8个）。 Each nitrogen atom has two electrons hanging out there without partners, so, to solve the dilemma, each nitrogen atom shares two additional pairs of electrons, for a total of three pairs. hanging out把…伸出、挂出，上身伸出（窗外），闲荡 每个氮原子都有两个未成对电子，所以，为了解决这一矛盾，每个氮原子共用另外两对电子，共3对电子

.：.N N：In drawing the nitrogen molecule (N2), we have placed all the

electrons being shared by the two atoms in the space between the two atoms.

being shared by the two atoms分词短语做定语

写氮分子（N2）时，我们把两个原子的所有的共用电子都写在两个原子中间。

Each nitrogen atom has now satisfied the octet rule. 每个氮原子都满足了八耦体规则。

A molecule in which three pairs of electrons (a total of six individual electron) are being shared is said to contain a triple bond. in which three pairs of electrons (a total of six individual electron) are being shared定语从句 triple bond三键

一个分子共享三对电子（共6个单个电子）被称为含有三键。 Each nitrogen atom also has an unshared pair of electrons. 每个氮原子还含有一对孤对电子。

Note that we could have drawn the unshared pair of electrons above or below the atomic symbol. atomic symbol 元素符号

注意我们可以把孤对电子写在元素符号的上方或下方。 Such a drawing would represent the same molecule. 这些写法代表相同的分子。