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  • 定期趋势:电子亲近

    A red suitcase overflowing with neatly folded clothes, a hat, and a cap.

    Do you tend to overpack before going on trips?
    ::旅行前你是否倾向于过份包装?

    Packing for a trip can be very challenging.  What do you take with you?  Where will you be going and what will you need?  We usually pack too much (like the suitcase above) and then find it hard to close the suitcase.  When the suitcase is over-full, there is stress on the system and forces pushing the suitcase open.  When electrons are added to an , the increased negative charge puts stress on the electrons already there, causing energy to be released.
    ::包装旅行行李非常困难。 你带什么去? 你要去哪里? 你要去哪里? 你需要什么? 我们通常收拾太多行李(如上面的手提箱),然后很难关闭行李箱。 当行李箱过满时, 系统和推开行李箱的压力就会很大。 当电子被添加到一个egg 时, 增加的负电荷会给那里的电子造成压力, 从而释放能量。

    When electrons are removed from an atom, that process requires energy to pull the away from the nucleus .  Addition of an electron releases energy from the process.
    ::当电子从原子中去除时,该过程需要能量才能将核的能量拉离。加上电子,该过程释放出能量。

    Electron Affinity
    ::电子亲密度

    In most cases, the formation of an by the addition of an electron to a neutral atom releases energy. This can be shown for the chloride formation below:
    ::在大多数情况下,通过在中性原子中添加电子而形成一个电子释放能量。

    Cl + e -  → Cl - + energy
    ::Cl + e- Cl-+ 能源

    The energy change that occurs when a neutral atom gains an electron is called its electron affinity . When energy is released in a or process, that energy is expressed as a negative number. The figure below shows electron affinities in kJ/ mole for the representative .  Electron affinities are measured on atoms in the gaseous state and are very difficult to measure accurately.
    ::当中性原子获得电子时发生的能量变化被称为电子亲和。当能量在一个或工艺中释放时,能量以负数表示。下图显示代表的电子亲和度(kJ/mole)为kJ/mole。电亲和度(economs)在气体状态的原子上测量,很难精确测量。

    Table showing electron affinities in kJ/mole for representative elements, with halogens highlighted.
    Electron affinities (in kJ/mol) of the first five periods of the representative elements. Electron affinities are negative numbers because energy is released.

    The elements of the halogen group (Group 17) gain electrons most readily, as can be seen from their large negative electron affinities. This means that more energy is released in the formation of a halide ion than for the anions of any other elements. Considering electron configuration , it is easy to see why. The outer configuration of all is ns 2 np 5 . The addition of one more electron gives the halide ions the same electron configuration as a , which we have seen is particularly stable.
    ::卤素组(第17组)的元素最容易获得电子,从它们的大型负电子近亲中可以看出这一点。这意味着在形成卤化物离子的过程中释放的能量比其他元素的离子中释放的能量都多。考虑到电子配置,很容易看出原因。所有元素的外部配置为 ns2np5. 添加一个电子,使卤化物离子的配置与我们所看到的非常稳定。

    Period and group trends for electron affinities are not nearly as regular as for ionization energy . In general, electron affinities increase (become more negative) from left to right across a period and decrease (become less negative) from top to bottom down a group. However, there are many exceptions, owing in part to inherent difficulties in accurately measuring electron affinities.
    ::电子近亲的周期和群体趋势与电离化能源的周期和群体趋势不尽相同,一般来说,电子近亲在一段时间内从左向右增长(更负),从上到下下降(减负),但有许多例外,部分原因是在准确测量电子近亲方面存在内在困难。

     

     

     

     

    Summary
    ::摘要

    • Electron affinity is a measure of the energy released when an extra electron is added to an atom.
      ::电亲和度是测量原子添加额外电子时所释放的能量的量值。
    • Electron affinities are measured in the gaseous state.
      ::电子亲近度以气体状态测量。
    • In general, electron affinities become more negative as we move from left to right on the periodic table.
      ::一般来说,随着我们从左向右的周期表,电子亲近性变得更为消极。
    • In general, electron affinities become less negative from top to bottom of a group.
      ::一般来说,电子亲近性从一个群体的上到下越来越不那么消极。

    Review
    ::回顾

    1. Define “electron affinity."
      ::“电子姻亲关系”的定义。
    2. Does addition of an electron to a neutral atom require energy to be absorbed or released ?
      ::将电子添加到中性原子是否需要吸收或释放能量?
    3. Describe the general trend for electron affinity values moving from left to right on the periodic table.
      ::描述周期表中电子亲近值从左向右移动的总趋势。
    4. Describe the general trend for electron affinity values moving from top to bottom in a group on the periodic table.
      ::在周期表中的一组中,描述电子亲近值从上向下移动的总趋势。
    5. Why is more energy released in the formation of a halide ion than with other elements?
      ::为什么在卤化离子形成过程中释放的能量多于其他元素呢?