📚 Pre-U WJEC Chemistry: Core Knowledge Points Review | Pre-U WJEC 化学：核心知识点梳理
This article consolidates the essential topics required for the Pre-U WJEC Chemistry syllabus, linking concepts across physical, inorganic and organic chemistry. It serves as a structured revision guide to strengthen your understanding of the core principles.
本文梳理了 Pre-U WJEC 化学课程的核心知识点，将物理化学、无机化学和有机化学的重要概念串联起来，旨在帮助你有条理地巩固基础原理。
1. Atomic Structure and the Periodic Table | 原子结构与元素周期表
f chromium is [Ar] 3d⁵ 4s¹, not [Ar] 3d⁴ 4s², due to the extra stability of a half-filled d sub-shell.
电子排布遵循构造原理，轨道填充顺序为 1s → 2s → 2p → 3s → 3p → 4s → 3d。铬原子的电子构型是 [Ar] 3d⁵ 4s¹，而不是 [Ar] 3d⁴ 4s²，这是因为半充满的 d 亚层具有额外的稳定性。
Successive ionisation energies provide evidence for electron shells and the number of valence electrons. A sharp increase in ionisation energy indicates removal of an electron from an inner, more stable shell.
逐级电离能提供了电子层和价电子数的证据。电离能的大幅跃升表明电子开始从内层更稳定的壳层中被移走。
The periodic table is divided into s, p, d and f blocks according to the orbital being filled. Trends in atomic radius, first ionisation energy and electronegativity arise from the balance between nuclear charge, shielding and distance from the nucleus.
元素周期表根据填充的轨道分为 s 区、p 区、d 区和 f 区。原子半径、第一电离能和电负性的递变规律源于核电荷、屏蔽效应和电子离核距离之间的平衡。
2. Chemical Bonding and Structure | 化学键与结构
Ionic bonding involves the electrostatic attraction between oppositely charged ions formed by electron transfer. The strength of an ionic bond is measured by lattice enthalpy, which is determined through a Born–Haber cycle.
离子键是电子转移形成的带相反电荷离子间的静电吸引力。离子键的强度用晶格焓衡量，可通过玻恩-哈伯循环确定。
Covalent bonding arises from the sharing of electron pairs. The shape of a molecule is predicted by VSEPR theory: for example, methane (CH₄) is tetrahedral, ammonia (NH₃) is pyramidal and water (H₂O) is bent.
共价键源于电子对的共用。分子的形状可用价层电子对互斥理论 (VSEPR) 预测：例如甲烷 (CH₄) 是正四面体型，氨 (NH₃) 是三角锥型，水 (H₂O) 是 V 型。
Electronegativity differences lead to bond polarity. A molecule with polar bonds may be non-polar overall if the bond dipoles cancel by symmetry. Sigma bonds are formed by head-on orbital overlap, while pi bonds result from sideways overlap of p orbitals.
电负性差异导致键的极性。若键的偶极矩因对称性互相抵消，含有极性键的分子整体可能仍为非极性。σ 键由轨道头对头重叠形成，π 键则由 p 轨道肩并肩重叠形成。
3. Energetics and Thermochemistry | 化学能与热化学
where q = mcΔT. Standard conditions are 100 kPa and a stated temperature, typically 298 K.
反应的焓变 (ΔH) 可以通过量热实验测定，使用公式 q = mcΔT。标准条件是 100 kPa 压强和规定的温度（通常为 298 K）。
Hess’s law states that the total enthalpy change for a reaction is independent of the route taken. This allows calculation of ΔH for reactions that cannot be measured directly, using enthalpy changes of formation or combustion.
盖斯定律指出，一个反应的总焓变与反应途径无关。利用该定律，可以通过生成焓或燃烧焓数据计算难以直接测量的反应焓变。
Entropy (ΔS) is a measure of disorder. Gibbs free energy combines ΔH and ΔS: ΔG = ΔH – TΔS. A reaction is feasible when ΔG < 0.
熵 (ΔS) 是体系混乱度的量度。吉布斯自由能结合了焓变和熵变：ΔG = ΔH – TΔS。当 ΔG < 0 时，反应是热力学可行的。
4. Kinetics and Reaction Rates | 动力学与反应速率
B]ⁿ, where m and n are the orders with respect to each reactant. The overall order is m + n. The rate constant k depends only on temperature.
反应 A + B → 产物的速率方程形式为 速率 = k[A]ᵐ[B]ⁿ，其中 m 和 n 分别为各反应物的反应级数，总级数为 m + n。速率常数 k 仅取决于温度。
he Arrhenius equation links the rate constant to temperature and activation energy: k = Ae-Eₐ/RT. Eₐ is the minimum energy required for a collision to result in a reaction, and a catalyst provides an alternative pathway with lower Eₐ.
阿伦尼乌斯方程将速率常数与温度和活化能联系起来：k = Ae-Eₐ/RT。Eₐ 是碰撞能引发反应所需的最低能量，催化剂可提供活化能更低的替代反应路径。
Reaction mechanisms can be deduced from experimental rate data. The slowest step (rate-determining step) dictates the rate equation, and any species appearing in the rate equation must be involved up to and including that step.
反应机理可通过实验速率数据推断。最慢的一步（决速步）决定了速率方程，任何出现在速率方程中的物种必定参与了决速步及之前的过程。
5. Chemical Equilibria | 化学平衡
For a reversible reaction aA + bB ⇌ cC + dD, the equilibrium constant Kc is given by [C]ᶜ[D]ᵈ / [A]ᵃ[B]ᵇ. For gases, Kp is expressed in terms of partial pressures. Kc and Kp are temperature-dependent constants.
对于可逆反应 aA + bB ⇌ cC + dD，平衡常数 Kc 的表达式为 [C]ᶜ[D]ᵈ / [A]ᵃ[B]ᵇ。对气体反应，Kp 用分压表示。Kc 和 Kp 都是只随温度变化的常数。
Le Chatelier’s principle states that a system at equilibrium, when subjected to a change, will adjust to counteract the change. Increasing temperature favours the endothermic direction; increasing pressure favours the side with fewer gas molecules.
勒夏特列原理指出，处于平衡状态的体系在受到外界干扰时，会朝着削弱这种变化的方向移动。升高温度有利于吸热方向；增大压强有利于气体分子数减少的方向。
6. Acid-Base Equilibria | 酸碱平衡
Brø solution, the ionic product of water Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ mol² dm⁻⁶ at 298 K. pH = –log[H⁺].
根据布朗斯特-劳里酸碱理论，酸是质子给体，碱是质子受体。在水溶液中，水的离子积 Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ mol² dm⁻⁶ (298 K)。pH = –log[H⁺]。
a weak acid and its conjugate base (or a weak base and its conjugate acid). The Henderson–Hasselbalch equation is pH = pKa + log([A⁻]/[HA]).
弱酸和弱碱发生部分解离，用 Ka 和 Kb 表征其强度。缓冲溶液能够抵抗 pH 变化，由弱酸及其共轭碱（或弱碱及其共轭酸）组成。亨德森-哈塞尔巴尔赫方程为 pH = pKa + log([A⁻]/[HA])。
7. Redox Reactions and Electrochemistry | 氧化还原与电化学
Oxidation is an increase in oxidation number, reduction a decrease. Half-equations can be combined to give a full redox equation, balancing electrons and atoms in acidic or alkaline media.
氧化数升高是氧化，氧化数降低是还原。将半反应式合并可得到完整的氧化还原方程式，并在酸性或碱性介质中配平电子和原子。
referenced against the standard hydrogen electrode. The cell potential E°cell = E°(right) – E°(left). A positive E°cell indicates a thermodynamically feasible reaction.
标准电极电势 (E°) 衡量半电池获电子的倾向，以标准氢电极为基准。电池电势 E°cell = E°(右) – E°(左)。E°cell 为正值表示反应在热力学上可行。
ed depends on the charge passed: Q = It, and the amount of electrons is Q / 96500 C mol⁻¹.
电解利用电能驱动非自发的氧化还原反应。放电的物质质量取决于通过的电量：Q = It，电子的物质的量为 Q / 96500 C mol⁻¹。
8. Transition Metals and Coordination Chemistry | 过渡金属与配位化学
Transition metals are d-block elements that form at least one stable ion with a partially filled d sub-shell. Characteristic properties include variable oxidation states, coloured compounds and catalytic activity.
过渡金属是 d 区元素，能形成至少一种含有部分填充 d 亚层的稳定离子。其特性包括可变氧化态、形成有色化合物以及催化活性。
Ligands are species that donate a lone pair to a central metal ion, forming a coordination complex. Common ligands include water, ammonia and chloride ions. The coordination number and shape depend on the metal ion and ligand size.
配体是向中心金属离子提供孤对电子的物种，形成配位化合物。常见配体有水、氨和氯离子。配位数和空间构型取决于金属离子和配体的大小。
Isomerism in complexes includes geometrical (cis/trans) and optical isomerism. Ligand substitution reactions can be used to identify metal ions, and the colour of complexes arises from d–d electron transitions absorbing visible light.
配合物的异构现象包括几何异构（顺/反式）和旋光异构。配体取代反应可用于鉴定金属离子，配合物的颜色源于 d–d 电子跃迁吸收了可见光。
9. Introduction to Organic Chemistry | 有机化学基础
Organic compounds are classified by functional groups, such as alkanes, alkenes, alcohols, aldehydes, ketones, carboxylic acids and amines. Systematic IUPAC naming follows the rules of longest chain, lowest locants and alphabetical order of substituents.
有机化合物按官能团分类，如烷烃、烯烃、醇、醛、酮、羧酸和胺。系统命名法 (IUPAC) 遵循最长碳链、最低位次编号以及取代基按字母顺序排列的规则。
merism (due to restricted rotation around a C=C bond) and optical isomerism (chiral centres with four different groups).
结构异构是指分子式相同但原子连接顺序不同的现象。立体异构包括 E/Z 异构（因 C=C 双键旋转受阻）和旋光异构（手性中心连有四个不同基团）。
10. Organic Reaction Mechanisms and Functional Groups | 有机反应机理与官能团
Alkanes undergo free-radical substitution with halogens in the presence of UV light, proceeding through initiation, propagation and termination steps.
烷烃在紫外光照射下与卤素发生自由基取代反应，经过链引发、链增长和链终止步骤。
Alkenes react by electrophilic addition. The π bond is electron-rich and attracts electrophiles such as HBr, Br₂ or H₂SO₄. Markovnikov’s rule explains the major product when adding HX to an unsymmetrical alkene.
烯烃发生亲电加成反应。π 键电子云密度高，可吸引亲电试剂，如 HBr、Br₂ 或 H₂SO₄。当不对称烯烃与 HX 加成时，马氏规则可以解释主要产物的生成。
Haloalkanes undergo nucleophilic substitution, either by SN1 or SN2 mechanisms depending on the class of haloalkane and the nucleophile. Primary haloalkanes favour SN2, tertiary favour SN1. Elimination competes with substitution and is favoured by hot, strong bases.
卤代烷发生亲核取代反应，按反应物和亲核试剂的不同分为 SN1 和 SN2 机理。伯卤代烷倾向 SN2，叔卤代烷倾向 SN1。消除反应与取代反应竞争，在热浓强碱条件下更易发生。
11. Analytical Techniques and Spectroscopy | 分析技术与波谱学
ation at characteristic wavenumbers. For example, C=O stretching absorbs near 1700 cm⁻¹; O–H in alcohols appears as a broad peak around 3200–3600 cm⁻¹.
红外光谱 (IR) 通过特征波数的红外吸收来识别官能团。例如，C=O 伸缩振动约在 1700 cm⁻¹ 吸收；醇中的 O–H 键在 3200–3600 cm⁻¹ 附近呈现宽峰。
Mass spectrometry determines the relative molecular mass and provides fragmentation patterns. The molecular ion peak (M⁺) gives the relative molecular mass, and fragment ions offer structural clues.
质谱用于测定相对分子质量并给出碎片离子模式。分子离子峰 (M⁺) 显示相对分子质量，碎片离子则提供结构线索。
Proton NMR spectroscopy gives information about the chemical environment of hydrogen atoms and the number of neighbouring protons (splitting patterns). Chemical shifts (δ) are measured relative to TMS, and the integration trace indicates the relative number of protons in each environment.
质子核磁共振波谱 (¹H NMR) 可以揭示氢原子的化学环境及相邻质子数（裂分模式）。化学位移 (δ) 以 TMS 为基准测定，积分曲线表示每种化学环境中质子的相对数目。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图