Atomic Structure and the Periodic Table | 原子结构与元素周期表

📚 Atomic Structure and the Periodic Table | 原子结构与元素周期表

Atomic structure and the periodic table form the foundation of IGCSE Science. Understanding how protons, neutrons and electrons are arranged, and how this arrangement determines chemical behaviour, is essential for both chemistry and physics topics. This revision guide covers the key ideas you need for your Edexcel IGCSE Science exam.

原子结构与元素周期表是IGCSE科学的基础。理解质子、中子和电子如何排列，以及这种排列如何决定化学性质，对于化学和物理主题都至关重要。本复习指南涵盖了Edexcel IGCSE科学考试所需的核心理念。

1. The Basic Particles of the Atom | 原子的基本粒子

An atom is the smallest part of an element that can take part in a chemical reaction. It consists of three subatomic particles: protons, neutrons and electrons. Protons and neutrons are found in the nucleus at the centre of the atom, while electrons move around the nucleus in energy shells.

原子是元素能参与化学反应的最小粒子。原子由三种亚原子粒子组成：质子、中子和电子。质子和中子位于原子中心的原子核内，而电子在核周围的能量壳层中运动。

Proton: positive charge, relative mass 1, found in the nucleus.
Neutron: no charge, relative mass 1, found in the nucleus.
Electron: negative charge, relative mass 1/1840, found in shells.

In a neutral atom, the number of protons equals the number of electrons, so the total charge is zero.

在电中性的原子中，质子数等于电子数，因此总电荷为零。

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

Every element has a unique atomic number (also called proton number). This is the number of protons in the nucleus. The mass number (nucleon number) is the total number of protons and neutrons in the nucleus.

每种元素都有唯一的原子序数（也称质子数）。这是原子核中的质子数目。质量数（核子数）是原子核中质子与中子的总和。

Mass number = Number of protons + Number of neutrons

You can calculate the number of neutrons by subtracting the atomic number from the mass number.

你可以通过从质量数中减去原子序数来计算中子数。

For example, carbon-12 has a mass number of 12 and an atomic number of 6, so it has 6 neutrons.

例如，碳-12的质量数为12，原子序数为6，因此它有6个中子。

3. Isotopes | 同位素

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers.

同位素是同一元素中具有相同质子数但不同中子数的原子。这意味着它们的原子序数相同，但质量数不同。

For example, chlorine-35 and chlorine-37 are both isotopes of chlorine. They have 17 protons, but 18 and 20 neutrons respectively.

例如，氯-35和氯-37都是氯的同位素。它们都有17个质子，但分别有18个和20个中子。

Isotopes of the same element have identical chemical properties because chemical behaviour depends on the electron arrangement, which is the same. However, their physical properties may differ slightly, such as mass and density.

同一种元素的同位素具有相同的化学性质，因为化学行为取决于电子排布，而电子排布是相同的。然而，它们的物理性质可能略有不同，例如质量和密度。

4. Electronic Configuration | 电子排布

Electrons are arranged in energy shells, also called energy levels. The first shell can hold up to 2 electrons, the second shell up to 8, and the third shell up to 8 (for the first 20 elements).

电子排列在能量壳层中，也称为能级。第一层最多容纳2个电子，第二层最多8个，第三层最多8个（对于前20号元素）。

To write an electronic configuration, you distribute the total number of electrons into shells, starting from the shell closest to the nucleus. For example, sodium has 11 electrons, so its electronic configuration is 2,8,1.

要写出电子排布，你需要将总电子数从最靠近原子核的壳层开始分配到各层。例如，钠有11个电子，因此其电子排布为2,8,1。

Electronic configuration of sodium: 2, 8, 1

The number of electrons in the outer shell determines the reactivity of the atom and the type of bonding it can form.

最外层电子数决定了原子的反应活性以及它能形成的键合类型。

5. The Periodic Table Layout | 元素周期表结构

The periodic table arranges all known elements in order of increasing atomic number. Elements are arranged in rows called periods and columns called groups. The position of an element gives important information about its atomic structure.

元素周期表按原子序数递增的顺序排列所有已知元素。元素按行排列，称为周期；按列排列，称为族。元素的位置提供了关于其原子结构的重要信息。

Period number: tells you the number of occupied electron shells.
Group number: tells you the number of electrons in the outer shell (for main group elements).

For example, magnesium is in period 3 and group 2. This means it has 3 electron shells and 2 electrons in its outer shell.

例如，镁位于第三周期、第2族。这意味着它有3个电子壳层，最外层有2个电子。

6. Groups and Periods | 族和周期

Elements in the same group have similar chemical properties because they have the same number of outer-shell electrons. They show trends in physical and chemical properties as you go down the group.

同一族的元素具有相似的化学性质，因为它们最外层电子数相同。随着族往下移动，它们的物理和化学性质呈现趋势性变化。

In a period, elements show a gradual change from metallic to non-metallic character. As you go across a period, the number of protons and electrons increases, but the number of shells remains the same.

在同一周期中，元素从金属性向非金属性逐渐过渡。随着你在周期中从左向右移动，质子和电子的数量增加，但壳层数保持不变。

Knowing the group and period of an element allows you to predict its electronic configuration without memorising every atomic number.

知道元素的族和周期有助于你预测其电子排布，而无需记住每个原子序数。

7. Metals and Non-metals | 金属与非金属

The periodic table is roughly divided into metals on the left and non-metals on the right. Metals are typically shiny, malleable and good conductors of heat and electricity. Non-metals are usually dull, brittle and poor conductors.

元素周期表大致分为左侧的金属和右侧的非金属。金属通常有光泽、具有延展性，并且是良好的热和电导体。非金属通常暗淡、易碎且导电性差。

In chemical reactions, metals tend to lose electrons to form positive ions, while non-metals tend to gain electrons to form negative ions.

在化学反应中，金属倾向于失去电子形成正离子，而非金属倾向于获得电子形成负离子。

Some elements, such as carbon and silicon, are metalloids and show properties between metals and non-metals.

一些元素，如碳和硅，是类金属，表现出介于金属和非金属之间的性质。

8. Group 1 Alkali Metals | 第1族碱金属

Group 1 elements are called the alkali metals. They include lithium, sodium, potassium, rubidium and caesium. They all have one electron in their outer shell, which makes them highly reactive.

第1族元素被称为碱金属。它们包括锂、钠、钾、铷和铯。它们最外层都有一个电子，这使得它们非常活泼。

As you go down the group, the atoms get larger and the outer electron is further from the nucleus, so it is held less tightly. This means reactivity increases down the group.

随着族向下移动，原子变大，最外层电子离原子核更远，因此受到的束缚更弱。这意味着反应活性随族向下而增加。

Alkali metals react with water to produce hydrogen gas and an alkaline solution. For example, sodium reacts vigorously with water to form sodium hydroxide and hydrogen.

碱金属与水反应产生氢气和碱性溶液。例如，钠与水剧烈反应生成氢氧化钠和氢气。

2Na + 2H₂O → 2NaOH + H₂

9. Group 7 Halogens | 第7族卤素

Group 7 elements are called the halogens. They include fluorine, chlorine, bromine, iodine and astatine. They all have seven electrons in their outer shell and are non-metals.

第7族元素被称为卤素。它们包括氟、氯、溴、碘和砹。它们最外层都有七个电子，且是非金属。

As you go down the group, the atoms become larger and the outer shell is further from the nucleus, making it easier to gain an electron. However, reactivity actually decreases down the group because the incoming electron is less attracted to the nucleus.

随着族向下移动，原子变大，最外层离原子核更远，因此更容易获得电子。然而，实际上反应活性随族向下而降低，因为新进入的电子受原子核的吸引更弱。

Halogens are diatomic molecules, such as Cl₂, Br₂ and I₂. They form ionic compounds with metals, where they gain one electron to form a halide ion with a charge of -1.

卤素是双原子分子，如Cl₂、Br₂和I₂。它们与金属形成离子化合物，其中卤素获得一个电子形成带-1电荷的卤离子。

10. Group 0 Noble Gases | 第0族稀有气体

Group 0 elements are the noble gases, including helium, neon, argon, krypton and xenon. They have a full outer shell of electrons, which makes them very stable and unreactive.

第0族元素是稀有气体，包括氦、氖、氩、氪和氙。它们具有全满的最外层电子，这使它们非常稳定且不活泼。

Noble gases exist as single atoms because they do not need to bond to achieve stability. Their low reactivity means they are used in applications where inert conditions are required, such as in lightbulbs or welding.

稀有气体以单原子形式存在，因为它们不需要成键就能达到稳定。它们极低的反应活性使其用于需要惰性条件的场合，例如灯泡或焊接。

Helium has two electrons in its only shell, which is full, while neon has eight electrons in its outer shell, also full.

氦在其唯一壳层中有两个电子，即全满；而氖在最外层有八个电子，也是全满。

11. Using the Periodic Table to Predict Properties | 利用周期表预测性质

The periodic table is a powerful tool for predicting unknown properties. If you know an element’s position, you can deduce its atomic structure, likely reactivity and type of bonding.

元素周期表是预测未知性质的有力工具。如果你知道元素的位置，就可以推断其原子结构、可能的反应活性以及键合类型。

For example, an element in group 5 and period 2 will have 5 outer electrons and 2 shells. Its atomic number would be 7 (since 2 + 5 = 7), which is nitrogen. You can also predict it is a non-metal and likely to form covalent bonds.

例如，位于第5族、第二周期的元素将有5个外层电子和2个壳层。其原子序数为7（因为2 + 5 = 7），即氮。你还可以预测它是非金属，并且可能形成共价键。

Understanding the periodic pattern helps you compare elements, such as which is more reactive, which has higher melting point, or which forms ions with what charge.

理解周期规律有助于你比较元素，例如哪种更活泼、哪种熔点更高，或者哪种形成带什么电荷的离子。

In your exam, you will often be asked to use the periodic table to answer questions about structure and properties. Make sure you can locate groups and periods quickly and interpret the information.

在考试中，你经常会被要求使用元素周期表来回答关于结构和性质的问题。确保你能快速定位族和周期并解读信息。

Published by TutorHao | Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

Atomic Structure and the Periodic Table | 原子结构与元素周期表