📚 Pre-U WJEC Chemistry: Vocabulary and Terminology Quick Memorisation Guide | Pre-U WJEC 化学：词汇术语速记指南
Mastering the extensive vocabulary of Pre-U WJEC Chemistry is essential for excelling in both theory and practical examinations. This guide breaks down key terms by topic, offers memorable mnemonics and etymological hints, and provides bilingual explanations to reinforce deep understanding. Each section alternates English and Chinese to help you internalise terminology quickly.
掌握 Pre-U WJEC 化学的广泛词汇对于在理论和实验考试中取得优异成绩至关重要。本指南按主题分解关键术语，提供朗朗上口的记忆法和词源提示，并用双语解释来强化深度理解。每个小节交替使用英文和中文，帮助你快速内化术语。
1. Atomic Structure & Quantum Numbers | 原子结构与量子数
🔹 Principal Quantum Number (n): Indicates the main energy level or shell. As n increases, the electron's energy and average distance from the nucleus increase. Mnemonic: 'n' simply stands for the number of the shell.
🔹 主量子数（n）： 表示主能级或电子层。n 越大，电子能量和离核平均距离越大。记忆法：'n' 代表壳层的编号。
🔹 Azimuthal Quantum Number (l): Defines the subshell shape; l = 0, 1, 2, 3 correspond to s, p, d, f orbitals. Remember 'l' as label for the shape: s-sphere, p-peanut (dumbbell), d-double peanut, f-flower (complex).
🔹 角量子数（l）： 定义亚层形状；l = 0, 1, 2, 3 对应 s, p, d, f 轨道。把 'l' 记作形状标签：s 球形，p 花生形（哑铃），d 双花生形，f 花朵形。
🔹 Magnetic Quantum Number (mₗ): Specifies the orbital orientation in space. For a given l, mₗ = –l, ..., 0, ..., +l. Think of 'mₗ' as mapping lobes' orientation.
🔹 磁量子数（mₗ）： 指定轨道在空间中的取向。给定 l，mₗ = –l, ..., 0, ..., +l。把 'mₗ' 联想为绘制瓣叶方向。
🔹 Spin Quantum Number (mₛ): Electron spin, either +½ or –½, often visualised as ↑ or ↓. Mnemonic: 'mₛ' dictates the spin motion.
🔹 自旋量子数（mₛ）： 电子自旋，可以是 +½ 或 –½，通常表示为 ↑ 或 ↓。记忆：'mₛ' 决定自旋方向。
2. Chemical Bonding & Molecular Shape | 化学键与分子形状
🔹 Sigma (σ) and Pi (π) Bonds: r than σ. All single bonds are σ; double bonds = 1σ + 1π; triple bonds = 1σ + 2π. Think of 'σ' as the strong skeleton.
🔹 σ键与π键： σ键由轨道头对头重叠形成，强且旋转对称。π键由侧面重叠形成，比σ键弱。单键全是σ键；双键=1σ+1π；三键=1σ+2π。把 'σ' 看作坚固的骨架。
🔹 Hybridisation: sp (linear, 180°), sp² (trigonal planar, 120°), sp³ (tetrahedral, 109.5°). Mnemonic: the number of 'p's plus one equals the number of attachments.
🔹 杂化轨道： sp（直线形，180°）、sp²（平面三角形，120°）、sp³（四面体形，109.5°）。记忆法：'p' 的数量加一等于连接基团数目。
🔹 VSEPR Theory: Valence Shell Electron Pair Repulsion – on. Lone pairs exert greater repulsion than bonding pairs, reducing bond angles. Mnemonic: 'VSEPR' = Very Simple Electron Pair Repulsion.
🔹 VSEPR理论： 价层电子对互斥理论——电子对互相排斥并排布以最小化斥力。孤对电子的排斥力大于成键电子对，从而压缩键角。记忆：'VSEPR' = 电子对互斥十分简单。
🔹 Electronegativity & Polarity: Electronegativity increases across periods and up groups. FONClBrIS (F>O>N>Cl>Br>I>S) is a useful mnemonic for common elements. A bond dipole arises when atoms differ in electronegativity.
🔹 电负性与极性： 电负性在同周期从左到右增大，同族从上到下减小。助记口诀 FONClBrIS 排序常见元素。当原子电负性不同时产生键偶极矩。
3. Energetics & Thermodynamics | 能量学与热力学
🔹 Enthalpy Change (ΔH): Heat change at constant pressure. Exothermic (ΔH < 0) releases heat; endothermic (ΔH > 0) absorbs heat. Standard enthalpy of formation (ΔHf°) of an element is zero.
🔹 焓变（ΔH）： 恒压下的热变化。放热（ΔH < 0）释放热量；吸热（ΔH > 0）吸收热量。元素的标准生成焓（ΔHf°）为零。
🔹 Hess's Law: The total enthalpy change for a reaction is independent of the route taken. Use enthalpy cycles and remember target equation manipulation.
🔹 盖斯定律： 反应总焓变与途径无关。使用焓循环，牢记要操作目标方程式。
🔹 Bond Enthalpy: rage energy required to break one mole of bonds in gaseous molecules. ΔH ≈ Σ(bonds broken) – Σ(bonds formed). Mnemonic: Breaking bonds absorbs energy, forming bonds releases energy.
🔹 键焓： 断裂气体分子中一摩尔键所需的平均能量。 ΔH ≈ Σ（断裂键能）– Σ（形成键能）。记忆：断裂键吸热，形成键放热。
🔹 Entropy (S) and Gibbs Free Energy (ΔG): Entropy measures disorder. Gibbs free energy change:
ΔG = ΔH – TΔS
A reaction is feasible when ΔG < 0. Mnemonic for feasibility: Go negative to go.🔹 熵（S）和吉布斯自由能（ΔG）： 熵度量混乱度。吉布斯自由能变：ΔG = ΔH – TΔS。当 ΔG < 0 时反应可行。可行性口诀：G为负才能行。
4. Kinetics & Reaction Rate Laws | 动力学与反应速率定律
🔹 Rate Equation: For a general reaction, rate = k[A]ᵐ[B]ⁿ. The exponents m and n are the orders with respect to each reactant; their sum is the overall order. Mnemonic: order is just the exponent in the rate law.
🔹 速率方程： 对于一般反应，速率 = k[A]ᵐ[B]ⁿ。指数 m 和 n 是各反应物的级数；它们的和为总级数。记忆：级数就是速率方程中的指数。
🔹 Rate Constant (k): Temperature-dependent proportionality factor. Use the Arrhenius equation: k = A e–Eₐ/RT, where A = frequency factor, Eₐ = activation energy. Higher T or lower Eₐ gives larger k.
🔹 速率常数（k）： 随温度变化的比例因子。使用阿伦尼乌斯方程：k = A e–Eₐ/RT，其中 A 为频率因子，Eₐ 为活化能。温度越高或活化能越低，k 越大。
🔹 Reaction Mechanisms: The rate-determining step (RDS) is the slowest step; the rate equation reflects the molecularity of the RDS. Intermediates do not appear in the rate law.
🔹 反应机理： 决速步（RDS）是最慢的步骤；速率方程反映决速步的分子数。中间体不出现在速率方程中。
5. Chemical Equilibria | 化学平衡
🔹 Dynamic Equilibrium: Forward and reverse rates equal; concentrations constant. Le Chatelier's principle predicts shift to counteract changes in concentration, pressure or temperature.
🔹 动态平衡： 正逆反应速率相等；浓度恒定。勒夏特列原理预测平衡会移动以抵消浓度、压强或温度的变化。
🔹 Equilibrium Constant (Kc and Kp): For aA + bB ⇌ cC + dD, Kc = [C]ᶜ[D]ᵈ / [A]ᵃ[B]ᵇ. For gases, use partial pressures: Kp = (PCᶜ PDᵈ)/(PAᵃ PBᵇ). Pure solids and liquids are omitted. Mnemonic: pressure partial, concentration c oncentration.
🔹 平衡常数（Kc 和 Kp）： 对于 aA + bB ⇌ cC + dD，Kc = [C]ᶜ[D]ᵈ/[A]ᵃ[B]ᵇ。对于气体用分压：Kp = (PCᶜ PDᵈ)/(PAᵃ PBᵇ)。纯固体和液体省略。记忆：Kp 对应分压，Kc 对应浓度。
🔹 Magnitude of K: K >> 1 means equilibrium lies far to the right (products favoured); K << 1 means reactants favoured. Temperature is the only factor that changes K.
🔹 K 值大小： K >> 1 表示平衡强烈偏向产物；K << 1 偏向反应物。只有温度能改变 K 值。
6. Acid-Base Chemistry & pH | 酸碱化学与pH
🔹 Brønsted-Lowry Definitions: Acid is a proton donor, base is a proton acceptor. Conjugate acid-base pairs differ by one H⁺. Think: acid adds H⁺, base binds H⁺.
🔹 布朗斯特-劳里定义： 酸是质子给体，碱是质子受体。共轭酸碱对仅差一个 H⁺。联想：酸增加 H⁺，碱束缚 H⁺。
🔹 pH Scale: pH = –log₁₀[H⁺]; pOH = –log₁₀[OH⁻]; at 25°C, Kw = [H⁺][OH⁻] = 1.0×10⁻¹⁴ and pH + pOH = 14. Mnemonic: the p stands for 'negative log'.
🔹 pH 标度： pH = –log₁₀[H⁺]；pOH = –log₁₀[OH⁻]；25°C 下 Kw = [H⁺][OH⁻] = 1.0×10⁻¹⁴，pH +
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