Atomic Structure | 原子结构

📚 Atomic Structure | 原子结构

Atomic structure is a fundamental topic in IGCSE Science. It explains how atoms are built, how they differ from one another, and why chemical reactions behave as they do. This revision guide covers the key concepts you need to master for your Edexcel examination.

原子结构是IGCSE科学中的基础主题。它解释了原子是如何构成的、原子之间如何不同，以及化学反应为何会如此进行。本复习指南涵盖了你在爱德思考试中需要掌握的关键概念。

1. The Model of the Atom | 原子模型

Atoms are the smallest particles of an element that retain its chemical properties. The modern model describes an atom as having a small, dense nucleus surrounded by electrons in shells (energy levels).

原子是保留元素化学性质的最小粒子。现代模型将原子描述为一个致密的小原子核，核外有电子在壳层（能级）中运动。

The nucleus contains protons and neutrons, collectively called nucleons. The electrons are negatively charged and move in regions of space called orbitals or shells.

原子核包含质子和中子，统称为核子。电子带负电荷，在称为轨道或壳层的空间中运动。

This model was developed over time, from Dalton’s solid sphere to Thomson’s plum pudding, Rutherford’s nuclear model, and Bohr’s planetary model.

这一模型经历了长期发展，从道尔顿的实心球体、汤姆逊的葡萄干布丁模型、卢瑟福的核式模型，到玻尔的行星模型。

2. Sub-atomic Particles | 亚原子粒子

There are three main sub-atomic particles: protons, neutrons and electrons. Their properties are crucial for understanding atomic behaviour.

主要有三种亚原子粒子：质子、中子和电子。它们的性质对于理解原子行为至关重要。

Proton – relative charge +1, relative mass 1. It determines the atomic number.
中子 – 相对电荷0，相对质量1。它有助于稳定原子核。
Electron – relative charge -1, relative mass 1/1836 (negligible). It occupies shells around the nucleus.

The number of protons in an atom defines the element. In a neutral atom, the number of electrons equals the number of protons.

原子中质子的数量决定了元素的种类。在中性原子中，电子数等于质子数。

For example, a carbon atom has 6 protons and 6 electrons, while an oxygen atom has 8 protons and 8 electrons.

例如，碳原子有6个质子和6个电子，而氧原子有8个质子和8个电子。

3. Atomic Number and Mass Number | 原子序数与质量数

The atomic number (Z) is the number of protons in the nucleus. The mass number (A) is the total number of protons and neutrons.

原子序数（Z）是原子核中的质子数。质量数（A）是质子和中子的总数。

You can calculate the number of neutrons using: neutrons = mass number − atomic number.

你可以通过以下公式计算中子数：中子数 = 质量数 − 原子序数。

neutrons = A − Z

In standard notation, the mass number is written as a superscript and the atomic number as a subscript before the element symbol, e.g. ²³Na, ¹²C.

在标准符号中，质量数作为上标、原子序数作为下标写在元素符号前，例如 ²³Na、¹²C。

For a neutral atom, the number of electrons equals the atomic number. For chlorine (Z=17, A=35), there are 17 protons, 17 electrons and 18 neutrons.

对于中性原子，电子数等于原子序数。对于氯（Z=17，A=35），有17个质子、17个电子和18个中子。

4. Isotopes | 同位素

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. They therefore have the same atomic number but different mass numbers.

同位素是同一元素的不同原子，它们具有相同的质子数但不同的中子数。因此它们具有相同的原子序数但不同的质量数。

For example, carbon-12 and carbon-14 are both carbon isotopes. Carbon-12 has 6 protons and 6 neutrons, while carbon-14 has 6 protons and 8 neutrons.

例如，碳-12和碳-14都是碳的同位素。碳-12有6个质子和6个中子，而碳-14有6个质子和8个中子。

Isotopes have the same chemical properties because they have the same number of electrons and the same electronic configuration. However, their physical properties (such as density or rate of diffusion) may differ due to different masses.

同位素具有相同的化学性质，因为它们具有相同的电子数和相同的电子排布。然而，它们的物理性质（如密度或扩散速率）可能因质量不同而有差异。

Some isotopes are radioactive, such as carbon-14 and iodine-131. These are used in medicine, archaeology and industry.

一些同位素具有放射性，例如碳-14和碘-131。它们被用于医学、考古学和工业中。

5. Electronic Configuration (Shells) | 电子排布（壳层）

Electrons occupy shells (energy levels) around the nucleus. Each shell has a maximum capacity: the first shell holds up to 2 electrons, the second and third shells hold up to 8 each.

电子占据原子核周围的壳层（能级）。每个壳层有最大容量：第一层最多2个电子，第二层和第三层各最多8个。

Electrons fill the innermost shells first. This is known as the Aufbau principle. The outermost shell is called the valence shell, and electrons there are valence electrons.

电子首先填充最内层。这称为构造原理。最外层称为价电子层，其中的电子是价电子。

For example, the electronic configuration of sodium (Na, Z=11) is 2, 8, 1. This means 2 electrons in the first shell, 8 in the second, and 1 in the third.

例如，钠（Na，Z=11）的电子排布是2, 8, 1。这表示第一层2个电子，第二层8个，第三层1个。

Na: 2, 8, 1

This arrangement determines how an atom bonds with others. Atoms are most stable when they have a full outer shell (typically 8 electrons, or 2 for helium).

这种排布决定了原子如何与其他原子成键。当原子具有满外层（通常8个电子，或氦的2个）时最稳定。

6. Formation of Ions | 离子的形成

Atoms can gain or lose electrons to achieve a full outer shell. When they do, they become charged particles called ions.

原子可以通过获得或失去电子来达到满外层。当发生这种情况时，它们会变成带电粒子，称为离子。

Metal atoms tend to lose electrons to form positive ions (cations). For example, sodium loses one electron to form Na⁺.

金属原子往往失去电子形成正离子（阳离子）。例如，钠失去一个电子形成Na⁺。

Na → Na⁺ + e⁻

Non-metal atoms tend to gain electrons to form negative ions (anions). For example, chlorine gains one electron to form Cl⁻.

非金属原子往往获得电子形成负离子（阴离子）。例如，氯获得一个电子形成Cl⁻。

Cl + e⁻ → Cl⁻

The number of electrons gained or lost is related to the group number in the periodic table. Group 1 elements form +1 ions, Group 2 form +2 ions, Group 6 form −2 ions, and Group 7 form −1 ions.

获得或失去的电子数与周期表中的族号有关。第1族元素形成+1离子，第2族形成+2离子，第6族形成−2离子，第7族形成−1离子。

7. Relative Atomic Mass | 相对原子质量

Relative atomic mass (Aᵣ) is the weighted average mass of an atom of an element compared with 1/12 of the mass of one atom of carbon-12. It accounts for the natural abundance of isotopes.

相对原子质量（Aᵣ）是元素的原子质量与碳-12原子质量的1/12相比的加权平均值。它考虑了同位素的自然丰度。

For example, chlorine has two stable isotopes: chlorine-35 (about 75%) and chlorine-37 (about 25%). The relative atomic mass is calculated as:

例如，氯有两种稳定同位素：氯-35（约75%）和氯-37（约25%）。相对原子质量计算如下：

Aᵣ = (35 × 75 + 37 × 25) / 100 = (2625 + 925) / 100 = 35.5

Therefore, the relative atomic mass of chlorine is 35.5, which is not a whole number because of the mixture of isotopes.

因此，氯的相对原子质量为35.5，因为它由不同同位素的混合物组成，所以不是整数。

You may be asked to calculate Aᵣ from percentage abundance data. Always remember to multiply each mass by its abundance, sum the results, and divide by 100.

你可能会被要求根据丰度百分比计算Aᵣ。请记住，将每个质量乘以其丰度，求和后再除以100。

8. Mass Spectrometry (Basic Idea) | 质谱法（基本概念）

Mass spectrometry is a technique used to measure the masses of atoms and molecules. It allows scientists to determine isotopic abundances and relative atomic masses very accurately.

质谱法是用于测量原子和分子质量的技术。它使科学家能够非常准确地测定同位素丰度和相对原子质量。

In a mass spectrometer, atoms are vaporised, ionised, accelerated, and then deflected by a magnetic field. Lighter or more charged ions are deflected more than heavier ones. The resulting mass spectrum shows peaks corresponding to different isotopes.

在质谱仪中，原子被汽化、电离、加速，然后被磁场偏转。较轻或电荷较多的离子比重的偏转更大。得到的质谱图上的峰对应不同的同位素。

The height of each peak is proportional to the relative abundance of each isotope. This information allows the relative atomic mass to be calculated.

每个峰的高度与各同位素的相对丰度成正比。利用这些信息即可计算相对原子质量。

9. The Periodic Table and Atomic Structure | 周期表与原子结构

The periodic table is arranged in order of increasing atomic number. Elements in the same group have the same number of outer electrons, which gives them similar chemical properties.

周期表按原子序数递增排列。同一族的元素具有相同的最外层电子数，因此具有相似的化学性质。

For example, Group 1 elements (alkali metals) all have one electron in their outer shell. They are highly reactive and form +1 ions. Group 7 elements (halogens) all have seven outer electrons and form −1 ions.

例如，第1族元素（碱金属）最外层都有一个电子。它们反应性很强，形成+1离子。第7族元素（卤素）最外层都有七个电子，形成−1离子。

Across a period, the number of electron shells remains the same, but the number of outer electrons increases from 1 to 8. This leads to trends in properties such as atomic size and reactivity.

在同一周期中，电子壳层数保持不变，但最外层电子数从1增加到8。这导致了原子大小和反应性等性质的趋势变化。

Understanding the link between electronic configuration and the periodic table is essential for predicting how elements react and bond.

理解电子排布与周期表之间的联系，对于预测元素如何反应和成键至关重要。

10. Exam Tips and Common Mistakes | 考试技巧与常见错误

Here are some important tips to help you avoid common errors in the exam.

以下是一些重要提示，帮助你在考试中避免常见错误。

Always remember: protons determine the element; neutrons affect the mass; electrons determine chemical behaviour.
切勿混淆原子序数和质量数。原子序数只代表质子数，质量数是质子数加中子数。
When writing electronic configurations, fill lower shells first. For calcium (Z=20), the configuration is 2, 8, 8, 2, not 2, 8, 10.
当书写电子排布时，先填充低能层。例如钙（Z=20）为2, 8, 8, 2，而不是2, 8, 10。
For isotopes, always mention same protons, different neutrons. The chemical properties are the same.
对于同位素，始终提到相同质子数、不同中子数。化学性质相同。
Use the correct notation for ions: Na⁺, Mg²⁺, Cl⁻, O²⁻. The charge comes from the number of electrons lost or gained.
正确书写离子符号：Na⁺、Mg²⁺、Cl⁻、O²⁻。电荷来自得失电子数。
When calculating relative atomic mass, use the given abundance percentages, not the mass numbers themselves as percentages.
计算相对原子质量时，使用给定的丰度百分比，而不是将质量数本身当作百分比。

Practice writing configurations and drawing ions. Keep your answers clear and use the correct scientific vocabulary.

练习书写电子排布和画出离子。保持答案清晰，使用正确的科学词汇。

Published by TutorHao | Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

Atomic Structure | 原子结构