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

In this revision article, we will explore the essential ideas of atomic structure and the periodic table, following the Edexcel IGCSE Science specification. These concepts explain how matter is built from tiny particles and why elements show repeating patterns in their properties.

在这篇复习文章中，我们将按照 Edexcel IGCSE 科学考试大纲，深入探讨原子结构和元素周期表的核心概念。这些概念解释了物质如何由微小粒子构成，以及元素的性质为什么会呈现周期性规律。

1. The Nuclear Model of the Atom | 原子的核模型

Atoms are the smallest particles of an element that still have the chemical properties of that element. The modern model we use is called the nuclear model of the atom.

原子是保持元素化学性质的最小粒子。我们现在使用的模型被称为原子的核模型。

In 1911, Ernest Rutherford and his team fired alpha particles at a very thin gold foil. Most particles passed straight through, but a few bounced back. This showed that the atom is mostly empty space, with a tiny, dense, positively charged nucleus at the centre.

1911年，欧内斯特·卢瑟福和他的团队用 α 粒子轰击极薄的金箔。大多数粒子直接穿过，但少数被反弹回来。这表明原子内部大部分是空的，而在中心存在一个极小、致密、带正电荷的原子核。

According to this model, the nucleus contains protons and neutrons. Very light, negatively charged electrons move around the nucleus in the empty space outside it.

根据这个模型，原子核内包含质子和中子。非常轻的、带负电荷的电子在核外的广阔空间中运动。

2. Subatomic Particles | 亚原子粒子

Atoms are made from three types of subatomic particle: protons, neutrons and electrons. It is important to know their relative masses and relative charges.

原子由三种亚原子粒子构成：质子、中子和电子。我们需要牢记它们的相对质量和相对电荷。

Particle / 粒子	Relative mass / 相对质量	Relative charge / 相对电荷	Location / 位置
Proton / 质子	1	+1	Nucleus / 原子核
Neutron / 中子	1	0	Nucleus / 原子核
Electron / 电子	1/1836 (almost 0)	-1	Outside nucleus / 核外

Protons and neutrons are found in the nucleus, so the nucleus has almost all the mass of the atom. Electrons are so light that we usually treat their mass as negligible.

质子和中子位于原子核内，因此原子核集中了原子几乎全部的质量。电子的质量非常小，通常可以忽略不计。

In a neutral atom, the number of electrons equals the number of protons. The positive charges and negative charges cancel out.

在电中性的原子中，电子数等于质子数。正电荷与负电荷相互抵消。

3. Atomic Number, Mass Number and Isotopes | 原子序数、质量数与同位素

The atomic number (Z) is the number of protons in the nucleus of an atom. This number defines which element the atom belongs to.

原子序数（Z）是原子核中的质子数。这个数字定义了该原子属于哪种元素。

The mass number (A) is the total number of protons and neutrons in the nucleus. The number of neutrons (N) can be calculated using this equation:

质量数（A）是原子核中质子数和中子数的总和。中子数（N）可以用以下公式计算：

A = Z + N

For example, a sodium atom has an atomic number of 11 and a mass number of 23. Therefore it has 11 protons and 12 neutrons.

例如，钠原子的原子序数为 11，质量数为 23。因此它有 11 个质子和 12 个中子。

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. For instance, carbon-12 and carbon-14 are isotopes of carbon.

同位素是同一元素的不同原子，它们具有相同质子数但不同中子数。例如，碳-12 和碳-14 是碳的同位素。

Isotopes can be written using the mass number as a superscript and the atomic number as a subscript before the chemical symbol. For example, carbon-14 is written as:

同位素可以用化学符号前的上标表示质量数、下标表示原子序数来书写。例如，碳-14 写成：

₁₄C ₆

Different isotopes of the same element have the same chemical properties, but their physical properties may be slightly different because their masses differ.

同一元素的不同同位素具有相同的化学性质，但由于质量不同，其物理性质可能略有差异。

4. Electronic Configuration | 电子排布

Electrons are arranged in energy levels, also called shells, around the nucleus. Each shell can hold a maximum number of electrons.

电子围绕原子核排列在能级上，也就是电子层中。每个电子层最多可容纳一定数量的电子。

The first shell can hold up to 2 electrons. / 第一层最多可容纳 2 个电子。
The second shell can hold up to 8 electrons. / 第二层最多可容纳 8 个电子。
The third shell can hold up to 8 electrons for the first 20 elements. / 对前 20 号元素来说，第三层最多可容纳 8 个电子。

To write the electronic configuration, we fill the inner shells first. For example, a sodium atom has 11 electrons. Its configuration is 2.8.1, meaning 2 electrons in the first shell, 8 in the second shell and 1 in the outer shell.

书写电子排布时，我们先填充内层电子壳层。例如，钠原子有 11 个电子，其排布为 2.8.1，表示第一层有 2 个电子，第二层有 8 个电子，外层有 1 个电子。

Electrons in the outermost shell are called valence electrons. They are responsible for the chemical behaviour of the element.

最外层电子称为价电子，它们决定元素的化学性质。

When drawing dot-and-cross diagrams, we place dots or crosses around the symbol of the element to show the electrons in the outer shell.

在绘制点叉电子图时，我们在元素符号周围用点或叉表示最外层电子。

5. The Periodic Table | 元素周期表

The periodic table arranges all known elements in order of increasing atomic number. It is divided into periods and groups.

元素周期表按原子序数递增的顺序排列所有已知元素，并分为周期和族。

A period is a horizontal row. Elements in the same period have the same number of electron shells.

周期是水平行。同一周期的元素具有相同数量的电子层。

A group is a vertical column. Elements in the same group have the same number of outer-shell electrons, which gives them similar chemical properties.

族是垂直列。同一族的元素具有相同的最外层电子数，因此化学性质相似。

The table also separates metals and non-metals. Most elements are metals on the left and in the middle; non-metals are on the right.

周期表还区分金属和非金属。大多数元素位于左侧和中间，是金属；非金属位于右侧。

For example, carbon is in Group IV (group 4) and has an electronic configuration of 2.4. Chlorine is in Group VII (group 7) with an electronic configuration of 2.8.7.

例如，碳位于第 IV 族（第 4 族），电子排布为 2.4。氯位于第 VII 族（第 7 族），电子排布为 2.8.7。

6. Group I Alkali Metals | 第 I 族碱金属

Group I elements, such as lithium, sodium and potassium, are called alkali metals. They are soft, low-density metals that react vigorously with water.

第 I 族元素，如锂、钠和钾，被称为碱金属。它们质软、密度低，能与水剧烈反应。

All alkali metals have one electron in their outer shell, so they lose this electron easily to form +1 ions.

所有碱金属在它们的电子最外层都有 1 个电子，因此它们很容易失去这个电子，形成 +1 离子。

Their reactivity increases as you go down the group. Potassium reacts more violently with water than sodium because its outer electron is further from the nucleus and is lost more easily.

越往下，反应活性越强。钾与水反应比钠更剧烈，原因是钾的外层电子离原子核更远，更容易失去。

When alkali metals react with water, they produce hydrogen gas and an alkaline hydroxide solution. For example, sodium reacts to form sodium hydroxide and hydrogen:

碱金属与水反应时，会产生氢气并生成碱性氢氧化物溶液。例如，钠与水反应生成氢氧化钠和氢气：

2Na + 2H₂O → 2NaOH + H₂

7. Group VII Halogens | 第 VII 族卤素

Group VII elements are known as halogens. They include fluorine, chlorine, bromine and iodine. These non-metals exist as molecules made of two atoms, for example Cl₂.

第 VII 族元素被称为卤素，包括氟、氯、溴和碘。这些非金属以双原子分子形式存在，例如 Cl₂。

At room temperature, chlorine is a pale green gas, bromine is a red-brown liquid and iodine is a dark grey solid that sublimes to a purple vapour.

在室温下，氯是浅绿色气体，溴是红棕色液体，碘是深灰色固体，加热时升华成紫色蒸气。

Halogens have seven outer-shell electrons. They tend to gain one electron to form -1 ions, such as Cl⁻.

卤素原子最外层有 7 个电子。它们容易获得 1 个电子，形成 -1 离子，例如 Cl⁻。

Going down the group, the halogens become less reactive. Fluorine is the most reactive halogen because its outer shell is closest to the nucleus and attracts an electron most strongly.

在同族中，从上到下卤素的活性逐渐减弱。氟是最活泼的卤素，因为其最外层电子离核最近，对电子的吸引力最强。

Halogens can take part in displacement reactions. A more reactive halogen can displace a less reactive one from a solution of its salt.

卤素可以参与置换反应。较活泼的卤素可以把较不活泼的卤素从其盐溶液中置换出来。

8. Group 0 Noble Gases | 第 0 族稀有气体

Group 0 elements are called noble gases. They include helium, neon and argon. These gases are colourless, very unreactive and exist as single atoms.

第 0 族元素被称为稀有气体，包括氦、氖和氩。这些气体无色、极不活泼，以单原子形式存在。

Their unreactivity arises from having a full outer shell of electrons. This stable arrangement gives them no tendency to gain, lose or share electrons.

它们不活泼是因为最外层电子已经排满。这种稳定结构使它们没有获得、失去或共享电子的倾向。

Helium has 2 outer electrons, while neon and argon have 8, giving them an octet configuration.

氦外层有 2 个电子，而氖和氩有 8 个电子，形成八电子稳定结构。

Because noble gases are so unreactive, they are used in lighting, welding and as protective atmospheres where reactions must be prevented.

由于稀有气体极不活泼，它们用于照明、焊接以及需要防止化学反应的保护气氛中。

9. Trends Across a Period | 同一周期的趋势

Moving from left to right across a period, the number of outer-shell electrons increases from 1 to 8. This changes the chemical nature of the elements.

在同一周期内从左向右移动，最外层电子数从 1 增加到 8，这使元素的化学性质发生变化。

Metallic character decreases across a period. On the left, elements are typical metals; on the right, they are typical non-metals.

在一个周期中，金属性逐渐减弱。左侧为典型金属，右侧为典型非金属。

Across a period, the atomic radius generally decreases. This is because the increasing number of protons pulls the outer electrons closer to the nucleus.

同一周期中，原子半径通常减小。这是因为质子数增加，把外层电子拉得离原子核更近。

For example, in Period 3, sodium is a metal, magnesium is a metal, aluminium is a metal, silicon is a metalloid, and phosphorus, sulfur, chlorine and argon are non-metals.

例如，在第三周期中，钠、镁、铝是金属，硅是准金属，磷、硫、氯和氩是非金属。

These trends help predict the properties of unknown elements based on their position in the periodic table.

这些趋势帮助我们根据元素在周期表中的位置预测未知元素的性质。

10. Ions and Simple Ionic Bonding | 离子与简单离子键

Atoms gain or lose electrons to obtain a full outer shell. When this happens, they become charged particles called ions.

原子通过得到或失去电子来获得满电子层。此时，它们成为带电粒子，称为离子。

Metals lose electrons to form positive ions (cations). For example, a sodium atom loses its outer electron to become Na⁺.

金属失去电子形成正离子（阳离子）。例如，钠原子失去其外层电子变为 Na⁺。

Non-metals gain electrons to form negative ions (anions). For example, a chlorine atom gains an electron to become Cl⁻.

非金属得到电子形成负离子（阴离子）。例如，氯原子得到一个电子变为 Cl⁻。

Ionic bonding occurs when oppositely charged ions attract each other with strong electrostatic forces. This happens between metals and non-metals.

当带相反电荷的离子之间通过强烈的静电引力相互吸引时，就形成了离子键。离子键通常出现在金属与非金属之间。

For example, sodium and chlorine react to form sodium chloride. The Na⁺ ion and Cl⁻ ion are held together in a giant ionic lattice structure.

例如，钠和氯反应生成氯化钠。Na⁺ 离子和 Cl⁻ 离子在巨大的离子晶格结构中紧密结合在一起。

Ionic compounds have high melting and boiling points because the electrostatic forces between ions are strong. They can conduct electricity when molten or dissolved in water, but not when solid.

离子化合物具有较高的熔点和沸点，因为离子之间的静电引力很强。它们在熔融状态或水溶液中能够导电，但在固态时不导电。

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