章节大纲

  • Two women play tennis, hitting a ball back and forth over the net.

    In a tennis match, two players keep hitting the ball back and forth. The ball bounces from one player to the other, over and over again. The ball keeps the players moving together on the court. What if the two players represented the nuclei of two atoms and the ball represented ? What would the back and forth movement of the ball represent? The answer is a covalent bond.
    ::在网球比赛中, 两个球员不停地前后打球。 球从一个球员向另一个球员反复反弹。 球让球员在球场上一起行动。 如果两个球员代表了两个原子的核和球代表的球呢? 球的前后运动代表着什么? 答案是共价债券。

    Sharing Electrons
    ::共享电

    A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. The shared electrons are attracted to the nuclei of both atoms. This forms a molecule consisting of two or more atoms. Covalent bonds form only between atoms of .
    ::共价联结是一种吸引力,它将两个原子合在一起,两个原子共享一对价值电子。共享电子被两个原子的核所吸引。这形成了由两个或两个以上原子组成的分子。共价联结只在原子之间形成。

    Covalent Compounds and Diatomic Elements
    ::共价化合物和糖尿病元素

    The two atoms that are held together by a covalent bond may be atoms of the same or different elements. When atoms of different elements form covalent bonds, a new substance, called a covalent compound , results. Water is an example of a covalent compound. A water molecule is modeled in the Figure . A molecule is the smallest particle of a covalent compound that still has the properties of the compound.
    ::当不同元素的原子形成共价债券时,新物质,称为共价化合物,结果。水是共价化合物的一个例子。图中以水分子为模型。分子是共价化合物中具有化合物特性的最小粒子。分子是共价化合物中具有化合物特性的最小粒子。

    Representation of the covalent bond formation between hydrogen and oxygen atoms in water.
    In water a molecule, hydrogen and oxygen atoms share a pair of electrons to form covalent bonds.

    Q: How many valence electrons does the oxygen (O) share with each hydrogen atom (H)? How many covalent bonds hold the water molecule together?
    ::问题:氧(O)与每个氢原子(H)共享多少价值电子?有多少共价联结将水分子放在一起?

    A: The oxygen atom shares one pair of valence electrons with each hydrogen atom. Each pair of shared electrons represents one covalent bond, so two covalent bonds hold the water molecule together.
    ::A:氧原子与每个氢原子共享一对价值电子。每对共有电子代表一个共价联结,因此两个共价联结将水分子放在一起。

    The diagram in the Figure shows an example of covalent bonds between two atoms of the same element, in this case two atoms of oxygen. The diagram represents an oxygen molecule, so it’s not a new compound. Oxygen normally occurs in diatomic (“two-atom”) molecules. Several other elements also occur as diatomic molecules: hydrogen, nitrogen, and all but one of the (fluorine, chlorine, bromine, and iodine). 
    ::图中的图示显示了同一个元素的两个原子之间的共价联系的示例,在这个例子中,两个氧原子。图表代表了氧分子,因此它不是一个新的化合物。氧通常出现在二原子(“二原子 ” ) 分子中。 其他几个元素也作为二解分子出现:氢、氮和除一种(氟、氯、溴和碘)以外的所有元素。

    Covalent bonds between two oxygen atoms sharing electrons.
    Electron sharing in an oxygen molecule

    Q: How many electrons do these two oxygen atoms share? How many covalent bonds hold the oxygen molecule together?
    ::问题:这两个氧原子共享多少个电子?有多少共价债券将氧分子放在一起?

    A: The two oxygen atoms share two pairs of electrons, so two covalent bonds hold the oxygen molecule together.
    ::A:两个氧原子共享两对电子, 所以两个共价债券将氧分子放在一起。

    Why Covalent Bonds Form
    ::为什么共价债券表

    Covalent bonds form because they give atoms a more stable arrangement of electrons. Look at the oxygen atoms in the Figure . Alone, each oxygen atom has six valence electrons. By sharing two pairs of valence electrons, each oxygen atom has a total of eight valence electrons. This fills its outer , giving it the most stable arrangement of electrons. The shared electrons are attracted to both oxygen nuclei, and this force of attraction holds the two atoms together in the oxygen molecule.
    ::共价债券形式, 因为它们给原子一个更稳定的电子组合。 看看图中的氧原子。 单独地看, 每个氧原子有六个等值电子。 通过共享两对等值电子, 每个氧原子共有八个等值电子。 这填满了它的外部, 使得它拥有最稳定的电子组合。 共享电子被两个氧核所吸引, 这种吸引力将氧分子中的两个原子放在一起。

    Summary
    ::摘要

    • A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. Covalent bonds form only between atoms of nonmetals.
      ::共价债券是一种吸引力,它将两个原子合在一起,这些原子共享一对价值电子。 共价债券只在非金属原子之间形成。
    • The two atoms that are held together in a covalent bond may be atoms of the same element or different elements. When atoms of different elements bond together, it forms a covalent compound.
      ::在共价保证金中存放在一起的两个原子可能是同一元素或不同元素的原子,当不同元素的原子结合在一起时,它形成共价化合物。
    • Covalent bonds form because the shared electrons fill each atom’s outer energy level and this is the most stable arrangement of electrons.
      ::共价债券的形式是,共享电子填充每个原子的外部能量水平,这是最稳定的电子组合。

    Review
    ::回顾

    1. What is a covalent bond?
      ::什么是共价债券?
    2. Nitrogen is a diatomic element with five valence electrons. Create a model of a molecule of nitrogen.
      ::氮是一种含有五种等值电子的亚原子元素。 生成一个氮分子模型。
    3. Which of the following represents a covalent compound?
      1. O 2
        ::氧2
      2. CO 2
        ::CO2 CO2
      3. Cl 2
        ::Cl2 Cl2
      4. NaCl
        ::NaCl 纳居器

      ::下列哪一种是共价化合物? O2 CO2 Cl2 NaCl

    Explore More
    ::探索更多

    Watch the video about covalent bonding and then answer the questions below. 
    ::观看关于共价连接的视频,然后回答下面的问题。

     

     

     

    1. How can you tell the number covalent bonds the atoms of an element can form?
      ::您如何分辨出元素原子能构成的共价键数 ?
    2. How many covalent bonds can nitrogen form? How many covalent bonds can chlorine form?
      ::氮能形成多少共价债券?氯能形成多少共价债券?
    3. How do ionic bonds differ from covalent bonds in terms of how electrons are shared ?
      ::离子债券与共价债券在电子如何共享方面有何不同?
    4. Why do nonmetals near the right side of the periodic table tend to form diatomic molecules with themselves, like Cl 2 or O 2 ?
      ::为什么在周期表右侧的非金属往往会自己形成二解分子,如Cl2或O2?