📚 AQA GCSE Chemistry: Atomic Structure and the Periodic Table | AQA GCSE 化学：原子结构与元素周期表
This article covers the core ideas from the AQA GCSE Chemistry Student Book by Lawrie Ryan. It explains atomic structure, the development of the periodic table, and the trends in Groups 1, 7 and 0.
本文覆盖 Lawrie Ryan 所著 AQA GCSE 化学学生用书的核心内容，解释原子结构、元素周期表的发展以及第1族、第7族和第0族的递变规律。
1. Elements, Compounds and Mixtures | 元素、化合物与混合物
An element is a substance made of only one type of atom, so it cannot be broken down into simpler substances by chemical means.
元素是由同一种原子组成的物质，因此不能通过化学方法分解成更简单的物质。
A compound contains two or more elements chemically combined in fixed proportions, and its properties are usually different from those of its constituent elements.
化合物由两种或两种以上元素按固定比例化学结合而成，其性质通常与组成元素的性质不同。
A mixture contains two or more elements or compounds that are not chemically combined, so each part keeps its own chemical properties.
混合物含有两种或两种以上没有化学结合的元素或化合物，因此各组分保持各自的化学性质。
Mixtures can be separated by physical techniques such as filtration, crystallisation, simple distillation, fractional distillation and chromatography.
混合物可以通过过滤、结晶、简单蒸馏、分馏和色谱等物理方法进行分离。
For example, rock salt is a mixture of sand and salt; adding water, filtering and then evaporating the water leaves pure salt.
例如，岩盐是沙子和盐的混合物；加水溶解、过滤再蒸发水分，就可以得到纯的盐。
2. Development of Atomic Theory | 原子理论的发展
John Dalton described atoms as tiny, indivisible solid spheres, but later experiments showed that atoms contain smaller subatomic particles.
约翰·道尔顿将原子描述为极小的、不可分割的实心球体，但后来的实验证明原子内部含有更小的亚原子粒子。
J. J. Thomson discovered the electron and proposed the plum pudding model, in which negative electrons were embedded in a positive mass of matter.
J. J. 汤姆孙发现了电子，并提出了梅子布丁模型，即负电子嵌在带正电的物质中。
Rutherford's alpha particle scattering experiment showed that most alpha particles passed straight through gold foil, but a few were deflected or bounced back.
卢瑟福的α粒子散射实验表明，大多数α粒子直接穿过金箔，但少数发生偏转或被反弹回来。
This led to the nuclear model, where the atom is mostly empty space with a small, dense, positively charged nucleus at its centre.
由此提出了核模型，即原子内部大部分是空的，中心有一个很小、密度很大且带正电的原子核。
Niels Bohr later proposed that electrons orbit the nucleus in fixed energy levels or shells, which explained why electrons do not spiral into the nucleus.
尼尔斯·玻尔后来提出电子在固定的能级或壳层中绕核运动，这解释了电子为何不会坠入原子核。
James Chadwick discovered the neutron, which has no charge and adds mass to the nucleus without changing the atomic number.
詹姆斯·查德威克发现了中子，中子不带电荷，能在不改变原子序数的情况下增加原子核的质量。
3. Subatomic Particles and Atomic Number | 亚原子粒子与原子序数
Protons have a relative charge of +1 and a relative mass of 1; neutrons have a relative charge of 0 and a relative mass of 1.
质子相对电荷为+1，相对质量为1；中子相对电荷为0，相对质量为1。
Electrons have a relative charge of -1 and a relative mass that is so small it is usually taken as zero in GCSE calculations.
电子相对电荷为-1，相对质量非常小，在 GCSE 计算中通常视为 0。
The atomic number is the number of protons in an atom, and it determines which element the atom belongs to.
原子序数是原子中的质子数，它决定了原子属于哪一种元素。
The mass number is the total number of protons and neutrons in the nucleus of an atom.
质量数是原子核内质子数与中子数的总和。
number of neutrons = mass number - atomic number
中子数 = 质量数 - 原子序数
In an atom, the number of protons equals the number of electrons, so the overall charge is zero.
在原子中，质子数等于电子数，因此整体电荷为零。
If an atom gains or loses electrons, it becomes a charged particle called an ion.
如果原子得到或失去电子，就会变成带电粒子，称为离子。
4. Isotopes and Relative Atomic Mass | 同位素与相对原子质量
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
同位素是同一种元素的原子，具有相同的质子数但中子数不同。
Because isotopes have the same number of electrons, they have identical chemical properties but slightly different masses.
由于同位素具有相同的电子数，它们的化学性质相同，但质量略有不同。
Relative atomic mass is an average value that takes into account the masses and abundances of all the naturally occurring isotopes of an element.
相对原子质量是考虑了元素所有天然同位素的质量和丰度后的平均值。
For example, chlorine has two common isotopes: 75% Cl-35 and 25% Cl-37, giving a relative atomic mass of 35.5.
例如，氯有两种常见同位素：75% 的 Cl-35 和 25% 的 Cl-37，因此相对原子质量为 35.5。
Aᵣ = (75 × 35 + 25 × 37) ÷ 100 = 35.5
The term relative atomic mass means the average mass of all isotopes compared with 1/12 the mass of one carbon-12 atom.
相对原子质量是指所有同位素的平均质量与一个碳-12 原子质量的 1/12 相比所得的比值。
5. Electronic Structure | 电子排布
Electrons occupy the lowest available energy levels first, because this arrangement is the most stable for the atom.
电子优先占据最低的可用能级，因为这种排布方式对原子来说最稳定。
The first electron shell can hold up to 2 electrons, the second shell up to 8 electrons, and the third shell also up to 8 electrons at GCSE level.
第一电子层最多容纳 2 个电子，第二层最多容纳 8 个电子，第三层在 GCSE 阶段也最多容纳 8 个电子。
Sodium has 11 electrons, so its electronic structure is 2,8,1; this explains why it is in Group 1 and Period 3.
钠有 11 个电子，因此其电子排布为 2,8,1；这解释了它位于第1族、第3周期。
The number of electrons in the outer shell determines the chemical properties of an element and its group number in the periodic table.
最外层电子数决定元素的化学性质及其在元素周期表中的族序数。
Atoms with full outer shells are very stable, so noble gases with full shells are extremely unreactive.
具有满外层电子结构的原子非常稳定，因此具有满电子层的稀有气体极不活泼。
6. History of the Periodic Table | 元素周期表的发展历史
John Newlands arranged elements by increasing atomic weight and noticed similar properties every eighth element, calling this the law of octaves.
约翰·纽兰兹按原子量递增的顺序排列元素，发现每第八个元素性质相似，称之为八音律。
Newlands's table failed for heavier elements because he did not leave gaps and some properties did not fit the pattern.
纽兰兹的元素表对较重元素不适用，因为他没有留下空位，而且有些性质不符合规律。
Dmitri Mendeleev arranged elements mainly by atomic mass but also by chemical properties, leaving gaps for undiscovered elements.
德米特里·门捷列夫主要按原子质量排列元素，但也结合化学性质，并为未发现元素留下了空位。
Mendeleev used his table to predict the properties of missing elements, and later discoveries matched his predictions very closely.
门捷列夫利用元素表预测了缺失元素的性质，后来发现的元素与他的预测非常吻合。
The modern periodic table arranges elements in order of increasing atomic number, which resolves inconsistencies found in earlier tables.
现代元素周期表按原子序数递增的顺序排列元素，解决了早期元素表中存在的不一致问题。
Elements in the same group have the same number of outer-shell electrons, so they have similar chemical properties.
同一族元素具有相同的最外层电子数，因此它们的化学性质相似。
7. Group 1: The Alkali Metals | 第1族：碱金属
Group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium; they are soft, shiny and have low density.
第1族金属包括锂、钠、钾、铷、铯和钫；它们质地柔软、有光泽且密度低。
Alkali metals react vigorously with water to form an alkaline metal hydroxide solution and hydrogen gas.
碱金属与水剧烈反应，生成碱性的金属氢氧化物溶液和氢气。
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
For example, sodium reacts with water to form sodium hydroxide and hydrogen gas, as shown by the equation above.
例如，钠与水反应生成氢氧化钠和氢气，反应方程式如上所示。
Reactivity increases down Group 1 because the outer electron is further from the nucleus and is more easily lost.
第1族向下递变时反应性增强，因为外层电子离原子核更远，更容易失去。
Group 1 metals react with oxygen to form metal oxides, and with chlorine to form white or colourless metal chloride salts.
第1族金属与氧气反应生成金属氧化物，与氯气反应生成白色或无色的金属氯化物盐。
Because alkali metals are so reactive, they are stored in oil to prevent contact with air and moisture.
由于碱金属非常活泼，它们被保存在油中，以防止与空气和水分接触。
8. Group 7: The Halogens | 第7族：卤素
The halogens are fluorine, chlorine, bromine, iodine and astatine; they exist as diatomic molecules such as F₂, Cl₂, Br₂ and I₂.
卤素包括氟、氯、溴、碘和砹；它们以双原子分子形式存在，如 F₂、Cl₂、Br₂ 和 I₂。
As you move down Group 7, the halogens become darker in colour, have higher density and higher melting and boiling points.
第7族向下递变时，卤素颜色变深、密度增大，熔点和沸点升高。
Reactivity decreases down Group 7 because the outer shell is further from the nucleus, so an incoming electron is attracted less strongly.
第7族向下递变时反应性降低，因为最外层离原子核更远，对进入的电子的吸引力较弱。
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
反应性较强的卤素可以从卤素盐的水溶液中置换出反应性较弱的卤素。
Cl₂(aq) + 2KBr(aq) → 2KCl(aq) + Br₂(aq)
For instance, chlorine displaces bromine from potassium bromide solution because chlorine is more reactive than bromine.
例如，氯可以从溴化钾溶液中置换出溴，因为氯比溴更活泼。
9. Group 0: The Noble Gases | 第0族：稀有气体
Group 0 elements are helium, neon, argon, krypton, xenon and radon; they are colourless gases at room temperature.
第0族元素包括氦、氖、氩、氪、氙和氡；它们在室温下是无色气体。
Noble gases have full outer shells of electrons, which makes them extremely unreactive or inert under normal conditions.
稀有气体具有满外层电子结构，因此在通常条件下极不活泼，呈惰性。
Boiling point and density increase down Group 0 because the atoms get larger and the intermolecular forces become stronger.
第0族向下递变时沸点和密度升高，因为原子变大，分子间作用力增强。
Helium is used in balloons because it is lighter than air, while argon is used in lamps because it stops the hot filament from burning.
氦用于气球是因为它比空气轻，氩用于灯泡是因为它能防止炽热灯丝被氧化。
10. Transition Metals and Comparison with Group 1 | 过渡金属及其与第1族的比较
Transition metals such as iron, copper and zinc are found in the central block of the periodic table between Groups 2 and 3.
过渡金属如铁、铜和锌位于元素周期表第2族和第3族之间的中央区域。
Compared with Group
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