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

Understanding atomic structure is the key to explaining the patterns in the Periodic Table. This article covers the essential ideas for your Edexcel IGCSE Science course: subatomic particles, electronic configuration, group trends, and how the Periodic Table is organised.

理解原子结构是解释元素周期表规律的关键。本文涵盖了Edexcel IGCSE科学课程的核心内容：亚原子粒子、电子排布、族的变化趋势以及周期表的组织方式。

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1. The Three Subatomic Particles | 三种亚原子粒子

Atoms are made of protons, neutrons and electrons. Protons carry a positive charge, neutrons are neutral, and electrons carry a negative charge. Protons and neutrons are found in the nucleus, while electrons orbit the nucleus in shells.

原子由质子、中子和电子构成。质子带正电荷，中子不带电，电子带负电荷。质子和中子位于原子核内，电子则在核外的电子壳层中运动。

• Proton: relative mass 1, relative charge +1.

  质子：相对质量1，相对电荷+1。

• Neutron: relative mass 1, relative charge 0.

  中子：相对质量1，相对电荷0。

• Electron: relative mass 1/1836, relative charge -1.

  电子：相对质量约为1/1836，相对电荷-1。

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

The atomic number (Z) is the number of protons in an atom. The mass number (A) is the total number of protons and neutrons. In a neutral atom, the number of electrons equals the number of protons.

原子序数（Z）是原子中的质子数。质量数（A）是质子数和中子数之和。在电中性的原子中，电子数等于质子数。

Mass number (A) = number of protons + number of neutrons

质量数（A） = 质子数 + 中子数

For example, sodium has atomic number 11 and mass number 23, so it contains 11 protons, 11 electrons and 23 – 11 = 12 neutrons.

例如，钠的原子序数为11，质量数为23，因此它含有11个质子、11个电子和23 – 11 = 12个中子。

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3. Electronic Configuration | 电子排布

Electrons occupy shells around the nucleus. The first shell holds up to 2 electrons, and the second and third shells hold up to 8 electrons each. The electronic configuration is written as numbers, e.g. sodium is 2,8,1.

电子在原子核周围的壳层中排布。第一壳层最多容纳2个电子，第二和第三壳层最多各容纳8个电子。电子排布用数字表示，例如钠的排布为2,8,1。

• Shell 1: maximum 2 electrons.

  第一壳层：最多2个电子。

• Shell 2: maximum 8 electrons.

  第二壳层：最多8个电子。

• Shell 3: maximum 8 electrons (for IGCSE).

  第三壳层：最多8个电子（IGCSE阶段）。

Elements in the same group have the same number of electrons in their outermost shell. This explains why they have similar chemical properties.

同一族的元素具有相同的最外层电子数。这解释了为什么它们具有相似的化学性质。

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4. The Structure of the Periodic Table | 周期表的结构

The Periodic Table arranges elements in order of increasing atomic number. Rows are called periods, and columns are called groups. There are 8 main groups, numbered from 1 to 7 and 0 (or 8).

周期表按照原子序数递增的顺序排列元素。横行称为周期，纵列称为族。主要有8个族，编号从1到7及0（或8）族。

Group	Outer electrons	族	最外层电子数
1	1	1（碱金属）	1
2	2	2（碱土金属）	2
3-7	3-7	3-7	3-7
0 (or 8)	8 (helium has 2)	0（或8）稀有气体	8（氦为2）

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5. Group 1: The Alkali Metals | 第1族：碱金属

Group 1 elements are soft metals with low density. They react vigorously with water to produce hydrogen gas and an alkaline solution. Their reactivity increases down the group.

第1族元素是柔软的低密度金属。它们与水剧烈反应，生成氢气和碱性溶液。其活泼性随着原子序数增大而增强。

2Na + 2H₂O → 2NaOH + H₂

Reactivity increases down the group because the outer electron is further from the nucleus, so it is more easily lost. The shielding effect of inner shells also reduces the attraction from the nucleus.

从上到下活泼性增强，因为最外层电子离核越来越远，更容易失去。内层电子的屏蔽效应也减弱了原子核对最外层电子的吸引。

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6. Group 7: The Halogens | 第7族：卤素

Group 7 elements are non-metals. They exist as diatomic molecules, such as F₂, Cl₂, Br₂ and I₂. They react with metals to form ionic salts. Their reactivity decreases down the group.

第7族元素是非金属。它们以双原子分子形式存在，如F₂、Cl₂、Br₂和I₂。它们与金属反应形成离子盐。其活泼性从上到下减弱。

• Fluorine: pale yellow gas, most reactive.

  氟：淡黄色气体，最活泼。

• Chlorine: green gas.

  氯：黄绿色气体。

• Bromine: red-brown liquid.

  溴：红棕色液体。

• Iodine: grey-black solid.

  碘：灰黑色固体。

Reactivity decreases down the group because the atoms get larger, making it harder to gain an extra electron to complete the outer shell.

从上到下活泼性减弱，因为原子半径增大，更难获得一个额外的电子来填满最外层。

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7. Group 0: The Noble Gases | 第0族：稀有气体

Group 0 elements are unreactive because they have a full outer shell of electrons. This full shell configuration is very stable. They exist as monatomic gases at room temperature and are used in lighting and welding.

第0族元素不活泼，因为它们的最外层电子已满。这种满壳层结构非常稳定。它们在室温下以单原子气体存在，用于照明和焊接。

Helium has 2 outer electrons, but this is also a full shell (the first shell holds only 2). Neon has 2,8, argon has 2,8,8, and so on.

氦的最外层有2个电子，但这也是满壳层（第一壳层最多只能容纳2个电子）。氖为2,8，氩为2,8,8，依此类推。

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8. Periods and Trends Across a Period | 周期及同周期变化趋势

Moving from left to right across a period, the number of protons increases, so the nuclear charge increases. Electrons are added to the same shell, which is pulled closer to the nucleus. Atomic radius decreases slightly, and the elements change from metals to non-metals.

在同一周期中从左到右，质子数增加，核电荷增大。电子加到同一壳层上，整个壳层被拉得更靠近原子核。原子半径略有减小，元素从金属变为非金属。

Property	Trend across a period	性质	同周期趋势
Metal character	Decreases	金属性	减弱
Non-metal character	Increases	非金属性	增强
Outer electrons	1 to 8	最外层电子数	从1增加到8

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9. Isotopes | 同位素

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

同位素是同一元素中具有相同质子数但不同中子数的原子。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 both have 6 protons, but carbon-12 has 6 neutrons while carbon-14 has 8 neutrons. Isotopes have identical chemical properties because they have the same electronic configuration, but their physical properties may differ.

例如，碳-12和碳-14都有6个质子，但碳-12有6个中子，碳-14有8个中子。同位素具有相同的化学性质，因为它们的电子排布相同，但物理性质可能不同。

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10. Ions and the Octet Rule | 离子与八隅体规则

Atoms tend to lose or gain electrons to achieve a stable full outer shell, often an octet of 8 electrons. Metals lose electrons to form positive ions (cations), while non-metals gain electrons to form negative ions (anions).

原子倾向于失去或获得电子以获得稳定的满外壳层，通常是8个电子的八隅体。金属失去电子形成带正电的阳离子，而非金属获得电子形成带负电的阴离子。

• Group 1 elements lose 1 electron to form 1+ ions.

  第1族元素失去1个电子形成1+离子。

• Group 2 elements lose 2 electrons to form 2+ ions.

  第2族元素失去2个电子形成2+离子。

• Group 7 elements gain 1 electron to form 1- ions.

  第7族元素获得1个电子形成1-离子。

• Group 6 elements gain 2 electrons to form 2- ions.

  第6族元素获得2个电子形成2-离子。

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11. Predicting Properties from Position | 根据位置预测性质

You can use the Periodic Table to predict properties of unknown elements. An element in Group 2 and Period 3 will have 3 shells and 2 outer electrons, so it will form a 2+ ion and react similarly to magnesium.

你可以利用周期表预测未知元素的性质。位于第2族和第3周期的元素将有3个壳层和2个最外层电子，因此它会形成2+离子，并与镁发生类似的反应。

Knowing the group helps predict the formula of its compounds. For example, chlorine in Group 7 combines with sodium in Group 1 to form NaCl, because 1+ and 1- charges balance.

知道族序数有助于预测其化合物化学式。例如，第7族的氯与第1族的钠结合形成NaCl，因为1+和1-电荷相互平衡。

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12. Exam Tips for IGCSE Science | IGCSE科学考试要点

When answering questions about atomic structure, always state the number of protons, neutrons and electrons clearly. Use the chemical symbol notation ^(A)_(Z)X when asked.

在回答有关原子结构的问题时，要清楚说明质子数、中子数和电子数。如果题目要求，请使用化学符号表示法^(A)_(Z)X。

Practice writing electronic configurations for the first 20 elements. Remember: calcium is 2,8,8,2, not 2,8,10. The third shell can hold more electrons at higher levels, but for IGCSE, 2,8,8,2 is correct for calcium.

练习写出前20号元素的电子排布。记住：钙是2,8,8,2，而不是2,8,10。第三壳层在更高层次可以容纳更多电子，但在IGCSE阶段，钙的排布写作2,8,8,2是正确的。

Always link trends in the Periodic Table to electron shells and nuclear charge. This will help you explain ‘why’ in exam questions, not just describe patterns.

始终将周期表中的变化趋势与电子壳层和核电荷联系起来。这将帮助你在考试中解释’为什么’，而不仅仅是描述规律。

Published by TutorHao | Science Revision Series | aleveler.com

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