AQA A-Level Chemistry Unit 1 – Foundation Chemistry Definitions
Mastering the foundational definitions in Unit 1 (CHEM1) is the key to unlocking the entire AQA A-Level Chemistry syllabus. This bilingual guide distills the essential terms every student must know — from atomic structure to organic chemistry basics. Let’s dive in! 🧪
掌握AQA化学Unit 1基础定义是打通整个A-Level化学的关键。 这份中英双语速查手册提炼了每一位考生必须掌握的核心理念——从原子结构到有机化学入门，一站式扫清概念障碍！
📖 1. Atomic Structure & Isotopes / 原子结构与同位素
Atomic number = number of protons in the nucleus. Mass number = protons + neutrons. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons — identical chemical properties, different physical properties.
原子序数 = 原子核中质子数。质量数 = 质子 + 中子。同位素：质子数相同、中子数不同的同种元素原子——化学性质相同，物理性质不同。
📖 2. Empirical vs Molecular Formula / 实验式与分子式
Empirical formula: the simplest whole-number ratio of atoms of each element in a compound. Molecular formula: the actual number of atoms of each element in a molecule. Know the difference — it’s a classic exam trap!
实验式：化合物中各元素原子的最简整数比。分子式：分子中各元素原子的实际数量。分清两者——这是考试中的经典陷阱！
📖 3. The Mole & Avogadro’s Constant / 摩尔与阿伏伽德罗常数
A mole is the SI unit for amount of substance. Avogadro’s constant (NA) = 6.02 × 10²³ mol⁻¹ — one mole. Every stoichiometry calculation in A-Level Chemistry traces back to this number.
摩尔 是物质的量的SI单位。阿伏伽德罗常数 = 6.02 × 10²³ mol⁻¹，即一摩尔物质所含的粒子数。A-Level化学中的所有化学计量计算都离不开这个数字。
📖 4. Bonding Types / 化学键类型
Ionic bond: electrostatic attraction between oppositely charged ions in a lattice. Covalent bond: a shared pair of electrons. Dative covalent bond: a covalent bond where both electrons come from the same atom. Metallic bond: a lattice of positive ions in a sea of delocalised electrons.
离子键：晶格中带相反电荷离子间的静电吸引力。共价键：共享电子对。配位共价键：两个电子均来自同一原子的共价键。金属键：正离子晶格沉浸在离域电子的”海洋”中。
📖 5. Electronegativity & Ionisation Energy / 电负性与电离能
Electronegativity: the ability of an atom to attract the bonding electrons in a covalent bond. First ionisation energy: the energy required to remove one mole of electrons from one mole of gaseous atoms. Both are fundamental to understanding periodic trends.
电负性：原子在共价键中吸引电子的能力。第一电离能：从一摩尔气态原子中移走一摩尔电子所需的能量。两者是理解元素周期律的基础。
🎯 学习建议 / Study Tips
- 📝 Flashcards are your best friend — write the term on one side and the definition on the other. Test yourself daily. / 抽认卡是最好的伙伴——正面写术语，背面写定义，每天自测。
- 🔗 Connect definitions to exam questions — many Unit 1 mark scheme answers are literally just these definitions. / 把定义与考题联系起来——Unit 1 评分标准中的许多答案就是这些定义本身。
- 🔄 Use the Feynman technique — explain each term out loud as if teaching a friend. If you stumble, revisit the definition. / 用费曼学习法——假装在教朋友，大声解释每个术语。卡住就回去复习。
- 📊 Group related terms — e.g., all bonding definitions together, all mole-related terms together. / 把相关术语归类——比如所有键合定义放一起，所有摩尔相关术语放一起。
📚 相关资源 / Related Resources
- 📘 AQA Unit 1 (CHEM1) — Full unit resources & past papers
- 📘 AQA Unit 2 (CHEM2) — Build on your Unit 1 foundation
- 🧪 AQA Unit 3 (CHM3T/CHM3X) — Practical skills assessment
- 📘 AQA Unit 4 (CHEM4) — Kinetics, equilibria & organic chemistry
- 📘 AQA Unit 5 (CHEM5) — Thermodynamics & periodicity
- 🔬 AQA Unit 6 (CHM6T/CHM6X) — Investigative skills
- 🧬 AQA Unit 1 (BIOL1) — Cross-reference with Biology
- ⚛️ AQA Unit 1 (PHYA1) — Particles, quantum & electricity
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