化学键介绍
视频：
化学键
离子键与共价键
视频：
离子键与共价键

化学键（chemical bond）是纯净物分子内或晶体内相邻两个或多个原子（或离子）间强烈的相互作用力的统称。使离子相结合或原子相结合的作用力通称为化学键。
离子键、共价键、金属键各自有不同的成因，离子键是通过原子间电子转移，形成正负离子，由静电作用形成的。共价键的成因较为复杂，路易斯理论认为，共价键是通过原子间共用一对或多对电子形成的，其他的解释还有价键理论，价层电子互斥理论，分子轨道理论和杂化轨道理论等。金属键是一种改性的共价键，它是由多个原子共用一些自由流动的电子形成的。

In this video we will compare ionic and covalent bonds.
本视频将对比离子键和共价键·
In order to understand ionic bonds we need to talk about ions first.
为了理解离子键,我们首先需要讨论离子·
Atoms are electrically neutral because they have equal numbers of both positively charged protons and negatively charged electrons.
原子是电中性的,因为它们拥有相等数量的正电荷质子和负电荷电子·
However an atom can become a charged particle called an ion if it gains or loses electrons.
然而,如果一个原子获得或失去电子,它可以变成带电粒子,称为离子·
If an atom gains electrons it acquires more negative charge.
如果一个原子获得电子,它会得到更多的负电荷·
As a result it becomes a negatively charged ion.
因此,它会变成带负电的离子·
Conversely if an atom loses electrons it loses some of its negative charge and becomes a positively charged ion.
相反,如果一个原子失去电子,它失去了一部分负电荷,变成带正电的离子·
The only way to get a positively charged ion is to lose negatively charged electrons.
获得带正电的离子唯一的方法是失去带负电的电子·
Remember you can't just add a proton to make a positive ion because changing the number of protons would change it into a different element.
记住,不能仅仅添加一个质子来制造正离子,因为改变质子数量会使它变成不同的元素·
Now let's talk about ionic bonds.
现在,我们来谈谈离子键·
Notice that this term contains the word ion.
注意,这个术语包含了"离子"一词·
That's because ionic bonds create ions out of electrically neutral atoms by the transfer of one or more valence electrons from one atom to another.
这是因为离子键通过从一个原子向另一个原子转移一个或多个价电子,将电中性的原子转化为离子·
Further electrically neutral atoms of elements whose outer shell is less than half filled with valence electrons tend to donate electrons
此外,外层电子不足半满的元素原子倾向于捐赠电子,
while atoms whose outer shell is more than half filled tend to attract electrons.
而外层电子超过半满的原子则倾向于吸引电子·
For example sodium and chlorine atoms are electrically neutral.
例如,钠和氯原子是电中性的·
Chlorine which only needs one electron to fill its outer shell strongly attracts sodium's single valence electron.
氯只需要一个电子来填满外层电子,因此它强烈吸引钠的单个价电子·
So these elements react to form a chemical bond creating sodium chloride.
因此,这些元素发生反应,形成化学键,生成氯化钠·
Sodium chloride otherwise known as table salt is an example of an ionically bonded compound.
氯化钠,也就是常见的食盐,是一个离子键结合的化合物示例·
This is because the electrically neutral sodium atom became a positively charged ion by losing its valence electron.
这是因为电中性的钠原子通过失去其价电子变成了带正电的离子·
And chlorine became a negatively charged ion by gaining this electron from sodium.
氯通过从钠获得电子,变成了带负电的离子·
So how do covalent bonds occur
那么,共价键是如何形成的呢?
The simplest substance that contains a covalent bond is a molecule of hydrogen gas also known as H2.
含有共价键的最简单物质是氢气分子,也叫做H2·
A hydrogen atom has only one electron in its outer shell which for this atom is also the shell nearest the nucleus.
一个氢原子只有一个电子在它的外层电子壳,这个壳层也是最靠近原子核的壳层·
This shell can hold a maximum of two electrons.
这个壳层最多可以容纳两个电子·
So atoms of hydrogen tend to pair up and share their electrons so that both atoms have their outer shell filled.
因此,氢原子倾向于配对并共享电子,以使两个原子的外层电子壳都得到填充·
As you can see covalent bonds occur when atoms share pairs of electrons.
如你所见,共价键在原子共享一对电子时形成·
In this molecule the hydrogen atoms form a single covalent bond.
在这个分子中,氢原子形成了一个单一的共价键·
Another example of a covalently bonded molecule is carbon dioxide or CO2.
另一个共价键结合的分子示例是二氧化碳,或CO2·
From its chemical formula you know that carbon dioxide contains one carbon atom and two oxygen atoms.
从其化学式中,你可以知道二氧化碳包含一个碳原子和两个氧原子·
Carbon has four valence electrons
碳有四个价电子,
and both oxygen atoms have six valence electrons.
而两个氧原子都有六个价电子·
But all three atoms would need eight electrons to fill their outer shells.
但是,所有三个原子都需要八个电子才能填满它们的外层电子壳·
So each oxygen atom shares a pair of electrons with the pair of electrons in carbon.
因此,每个氧原子与碳的电子对共享一对电子·
This results in two double covalent bonds where two pairs of electrons are shared between each atom.
这导致了两个双重共价键,其中每个原子之间共享两对电子·
To summarize the two main types of chemical bonds are ionic bonds and covalent bonds.
总结一下,化学键有两种主要类型,分别是离子键和共价键·
In ionic bonds one or more electrons are transferred from one atom to another.
在离子键中,一个或多个电子从一个原子转移到另一个原子·
In covalent bonds one or more pairs of electrons are shared between atoms.
在共价键中,一个或多个电子对在原子之间共享·
内容操作
视频
教程课件
单词卡片