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  • General

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  • 多原子离子共值保值

    Drawing Lewis structures for polyatomic ions is like extending laws to fit a new situation

    How do we extend basic principles?
    ::我们如何推广基本原则?

    The United States Supreme Court has the unenviable task of deciding what the law is.  This responsibility can be a major challenge when there is no clear principle involved or where there is a new situation not encountered before.  Chemistry faces the same challenge in extending basic concept to fit a new situation.  Drawing of Lewis structures for polyatomic uses the same approach, but tweaks the process a little to fit a somewhat different set of circumstances.
    ::美国最高法院承担着决定什么是法律的不可推崇的任务,当没有明确的原则或以前没有遇到新的情况时,这一责任可能是一项重大挑战。 化学在扩大基本概念以适应新情况时也面临着同样的挑战。 多方形的刘易斯结构的绘制使用同样的方法,但使这一过程稍有改变,以适应一些不同的情况。

    Polyatomic Ions
    ::多质离子

    Recall that a polyatomic ion is a group of atoms that are covalently bonded together and which carry an overall electrical charge. The ammonium ion, NH 4 + , is formed when a hydrogen ion (H + ) attaches to the lone pair of an ammonia (NH 3 ) molecule in a .
    ::多原子离子是一组原子,共价结合在一起,并带有总电荷。当氢离子(H+)附着在氨(NH3)分子的单对一分子上时,便形成氢离子(NH4+ ) 。

    Structure of the ammonium ion
    The ammonium ion.

    When drawing the Lewis structure of a polyatomic ion, the charge of the ion is reflected in the number of total in the structure.  In the case of the ammonium ion:
    ::当绘制多原子离子的刘易斯结构时,离子的荷载反映在结构中的总数中。

    1 N atom = 5   valence electrons 4 H atoms = 4 × 1 = 4   valence electrons subtract 1 electron for the 1 + charge of the ion total of 8 valence electrons in the ion

    ::1 N 原子=5 valence eenns4 H 原子=4x1=4 valence evalence evalence eurenssupptrate 1 电子,用于在离子中加装8 valence 电子共8个离子

    It is customary to put the Lewis structure of a polyatomic ion into a large set of brackets, with the charge of the ion as a superscript outside the brackets.
    ::通常的做法是将多原子离子的刘易斯结构置于一大批括号中,将离子作为上标的权责置于括号之外。

    Sample Problem: Lewis Electron Dot Structure of a Polyatomic Ion
    ::样本问题:多元离子的刘易斯电点结构

    Draw the Lewis dot structure for the sulfate ion.
    ::为硫酸盐离子绘制 Lewis点结构。

    Step 1: List the known quantities and plan the problem.
    ::第1步:列出已知数量并规划问题。

    Known
    ::已知已知

    molecular formula of sulfate ion = SO 4 2 − 1 S atom = 6   valence electrons 4 O atoms = 4 × 6 = 24   valence electrons add 2 electrons for the   2 −   charge of the ion total of 32 valence electrons

    ::硫酸盐离子=SO42-1 S原子=6 valence eenns4 O原子=4×6=24 valence eennsadd 2 economs 2 - 电离共32 valence eens

    The less electronegative sulfur is the central atom in the structure.  Place the oxygen atoms around the sulfur atom, each with a single covalent bond .  Distribute lone pairs to each oxygen atom in order to satisfy the .  Count the total number of atoms.  If there are too many electrons in the structure, make multiple bonds between the S and O.
    ::结构中的中心原子是电阴性硫磺。 将氧原子放在硫磺原子周围, 每个原子都有单一的共价连接。 将单对单对分配到每个氧原子, 以满足 。 计算原子的总数。 如果结构中存在太多电子, 则在 S 和 O 之间设置多个链接 。

    Step 2: Solve.
    ::步骤2:解决。

    Structure of the sulfate ion
    The sulfate ion.

    Step 3:  Think about your result.
    ::步骤3:想想你的结果。

    The Lewis structure for the sulfate ion consists of a central sulfur atom with four single bonds to oxygen atoms. This yields the expected total of 32 electrons, but there is still a small problem. As shown in the Figure , the charges in this structure are somewhat unbalanced.
    ::硫酸盐离子的刘易斯结构由中央硫磺原子组成,与氧原子有4个单一的连接点。这产生了32个电子的预期总数,但仍然存在一个小问题。如图所示,这一结构中的电荷有些不平衡。

    lesson content
    This structure uses all of the electrons, but a better structure brings as many of these charges to 0 as possible.

    Step 4: Balance charges.
    ::第4步:平衡费用。

    The correct Lewis structure for sulfate ( Figure ) moves electrons off two of the oxygen atoms to form an additional bond between them and the sulfur atom. This brings the charge of these three atoms to 0 and leaves -1 charges on the remaining two oxygen atoms. This structure is more stable because more atoms are neutral in charge.
    ::正确的硫酸盐 Lewis 结构( 图) 将两个氧原子的电子从两个氧原子移走, 形成它们与硫磺原子之间的额外连接。 这使得这三个原子的电荷达到0, 其余两个氧原子的电荷为1。 这个结构比较稳定, 因为更多的原子在负责中性 。

    lesson content
    The correct Lewis structure for sulfate shows two double bonds between the central sulfur atom and two of the outer oxygen atoms.

     

     

    Summary

    ::摘要

    • Lewis structures for polyatomic ions follow the same rules as those for other covalent compounds.
      ::多原子离子的刘易斯结构遵循与其他共价化合物相同的规则。

    Review
    ::回顾

    1. What are two characteristics of polyatomic ions?
      ::多原子离子的两个特征是什么?
    2. Which atom becomes the central atom in the structure?
      ::哪些原子成为结构的中心原子?
    3. Where is the charge on an ion placed in a lewis dot diagram?
      ::利维斯点形图中的离子上的电荷在哪里?