Chemical Bonding Exam Essentials | IB OCR 化学：化学键 考点精讲

📚 Chemical Bonding Exam Essentials | IB OCR 化学：化学键 考点精讲

Chemical bonding is the glue that holds matter together, determining the structure and properties of all substances. In IB and OCR Chemistry, mastering bonding is essential for understanding reactivity, shapes, and intermolecular forces. This article covers the key concepts, exam-style explanations, and common pitfalls to help you excel in your exams.

化学键是将物质结合在一起的力量，决定了所有物质的结构与性质。在IB和OCR化学中，掌握化学键对于理解反应性、分子形状和分子间作用力至关重要。本文涵盖核心概念、考试式的解释和常见陷阱，助你考试成功。

1. Ionic Bonding | 离子键

Ionic bonding occurs between metals and non-metals, forming a giant ionic lattice of alternating positive and negative ions.

离子键形成于金属与非金属之间，构成由正负离子交替排列的巨型离子晶格。

The electrostatic attraction between oppositely charged ions is strong, giving ionic compounds high melting and boiling points.

相反电荷离子之间的静电引力很强，使离子化合物具有高熔点和沸点。

In the solid state, ions are fixed in place, so ionic compounds do not conduct electricity. When molten or dissolved in water, the ions are free to move and act as charge carriers.

固态时，离子被固定在晶格中，因此离子化合物不导电。当熔融或溶于水时，离子能自由移动并充当电荷载体，从而导电。

Examples: NaCl (sodium chloride), MgO (magnesium oxide). The formula of an ionic compound shows the simplest ratio of ions to balance charges.

例子：NaCl (氯化钠)，MgO (氧化镁)。离子化合物的化学式表示平衡电荷所需的最简单离子比。

2Na(s) + Cl₂(g) → 2NaCl(s)

Common exam question: Explain why MgO has a higher melting point than NaCl. Answer: Mg²⁺ and O²⁻ have higher charges than Na⁺ and Cl⁻, leading to stronger electrostatic attraction, so more energy is required to overcome the forces.

常见考题：解释为什么MgO的熔点高于NaCl。答案：Mg²⁺和O²⁻所带电荷高于Na⁺和Cl⁻，导致更强的静电引力，因此需要更多能量来克服这些力。

2. Covalent Bonding | 共价键

Covalent bonding involves the sharing of electron pairs between two non-metal atoms to achieve a stable octet (or duplet for hydrogen).

共价键是通过两个非金属原子共享电子对以达到稳定八隅体（氢为两电子稳定结构）。

A single covalent bond shares one pair of electrons (e.g., H₂, Cl₂). A double bond shares two pairs (e.g., O₂: O=O), and a triple bond shares three pairs (e.g., N₂: N≡N).

单键共享一对电子（例如H₂、Cl₂）；双键共享两对电子（如O₂: O=O）；三键共享三对电子（如N₂: N≡N）。

The bond strength and length vary: triple bonds are shortest and strongest, single bonds are longest and weakest.

键的强度和长度各异：三键最短最强，单键最长最弱。

Coordinate or dative covalent bond: one atom provides both electrons of the shared pair; once formed, it is indistinguishable from a normal covalent bond. Example: NH₃ + BF₃ → H₃N-BF₃; also in the ammonium ion NH₄⁺.

配位键（或称给予-接受键）：一个原子提供共享电子对的两个电子；一旦形成，配位键与普通共价键无法区分。例子：NH₃ + BF₃ → H₃N-BF₃；以及铵根离子NH₄⁺。

3. Metallic Bonding | 金属键

Metallic bonding is the electrostatic attraction between a lattice of positive metal ions and a sea of delocalised electrons.

金属键是阳离子金属离子晶格与离域电子海之间的静电吸引。

This model explains metallic properties: malleability (layers slide over each other), ductility, high electrical and thermal conductivity (due to mobile electrons), and high melting points (strong attraction).

该模型解释了金属的性质：延展性（各层可相对滑动）、可锻性、高导电性和导热性（因为可移动电子），以及高熔点（强的吸引力）。

Alloys are mixtures of metals with other elements, often disrupting the regular lattice and reducing malleability but increasing strength (e.g., steel: iron + carbon).

合金是金属与其他元素的混合物，通常会破坏规则的晶格，降低延展性但增加强度（例如钢：铁+碳）。

4. Electronegativity and Bond Polarity | 电负性与键的极性

Electronegativity is the ability of an atom to attract the bonding pair of electrons in a covalent bond. Pauling scale: fluorine (4.0) is most electronegative.

Published by TutorHao | IB Chemistry Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）