Transition Metals in IGCSE CCEA Chemistry | IGCSE CCEA 化学：过渡金属考点精讲

📚 Transition Metals in IGCSE CCEA Chemistry | IGCSE CCEA 化学：过渡金属考点精讲

Transition metals are a block of metallic elements found in the middle of the periodic table. They form a bridge between the highly reactive Group 1 and 2 metals and the non-metals of Groups 13 to 18. For CCEA IGCSE Chemistry, you need to be able to describe their typical physical and chemical properties, compare them with Group 1 metals, recall their variable oxidation states, recognise the colours of important transition metal ions, explain their role as catalysts, and understand key examples such as iron and copper, including the corrosion of iron.

过渡金属是位于周期表中部的一组金属元素。它们在活泼的第1族、第2族金属与第13至18族的非金属之间起到桥梁作用。在CCEA IGCSE化学考试中，你需要能够描述它们典型的物理和化学性质，将它们与第1族金属进行对比，记住它们具有可变的化合价，识别重要过渡金属离子的颜色，解释它们的催化作用，并理解铁和铜等重要例子，包括铁的腐蚀。

1. Introduction to Transition Metals | 过渡金属简介

Transition metals are elements that have partially filled d orbitals in at least one of their common oxidation states. In the IGCSE context, we treat the block of metals from titanium to copper (and sometimes zinc) as typical transition metals, though zinc is often excluded because it does not form coloured compounds or have variable oxidation states under normal conditions.

过渡金属是指在至少一种常见氧化态下d轨道未完全充满的元素。在IGCSE范围内，我们通常把从钛到铜（有时也包括锌）的这一块金属视为典型的过渡金属，但锌经常被排除在外，因为在通常条件下它不生成有色化合物，也没有可变的化合价。

You should know that these elements are metals, they are all solid at room temperature (except mercury, which is liquid but not usually emphasised in the CCEA core), and they share a set of characteristic properties that set them apart from main-group metals such as sodium or magnesium.

你应当知道这些元素都是金属，在室温下均为固体（汞除外，它在室温下是液体，但CCEA的核心内容通常不强调这一点），并且它们共享一套特征性质，这使它们不同于钠、镁等主族金属。

2. Position in the Periodic Table | 周期表中的位置

The transition metals occupy the central block of the periodic table, between Group 2 and Group 13. They are often referred to as the d-block elements. When you look at a full periodic table, you will see a large rectangular area in the middle, starting from scandium (Z=21) to zinc (Z=30) in Period 4, and extending down through Periods 5, 6 and 7.

过渡金属占据周期表的中部区域，位于第2族和第13族之间。它们常被称为d区元素。观察完整的周期表时，你会看到中间有一大片矩形区域，从第4周期的钪（原子序数21）到锌（原子序数30），并向下延伸至第5、6和7周期。

In the CCEA exam, you may be asked to shade or identify the position of transition metals on a simplified periodic table outline. Remember they are found in the middle block, not to the left (Group 1 and 2) or far right (halogens and noble gases).

在CCEA考试中，你可能会被要求在简化的周期表轮廓上涂色或标出过渡金属的位置。记住它们位于中间的大区块，而不是在左边（第1、2族）或最右边（卤素和稀有气体）。

3. Physical Properties | 物理性质

Transition metals are typical metals but with several outstanding physical properties. They have high melting points and high boiling points. For example, iron melts at 1538 °C and copper at 1085 °C. They also have high densities: iron’s density is 7.87 g cm⁻³ and copper’s is 8.96 g cm⁻³. They are hard, strong, and malleable, meaning they can be hammered into shape without breaking.

过渡金属是典型的金属，但具有几项突出的物理性质。它们具有高熔点和高沸点。例如，铁的熔点为1538 °C，铜为1085 °C。它们还具有高密度：铁的密度为7.87 g cm⁻³，铜为8.96 g cm⁻³。它们坚硬、强度高且具有延展性，意味着可以被锤打成各种形状而不会断裂。

Transition metals are also excellent conductors of heat and electricity, which is why copper is widely used in electrical wiring. Their metallic bonding, involving the attraction between delocalised electrons and positive metal ions, is particularly strong because the transition metal atoms can release electrons from both their 4s and 3d orbitals, increasing the electron sea density.

过渡金属还是优良的热和电导体，这就是铜被广泛用于电线的缘故。它们的金属键涉及离域电子与正金属离子之间的吸引，这种键合特别强，因为过渡金属原子既可以释放4s轨道上的电子，也可以释放3d轨道上的电子，从而增大了电子海的密度。

In the CCEA specification, you do not need to explain conductivity in terms of d orbitals, but knowing that the strong metallic bonding leads to high melting points and hardness is very useful.

在CCEA考试大纲中，你不需要用d轨道来解释导电性，但知道强大的金属键导致高熔点和高硬度是非常有用的。

4. Comparison with Group 1 Metals | 与第1族金属的比较

One of the most common exam questions asks you to compare the physical and chemical properties of transition metals with those of Group 1 metals (alkali metals). The differences are striking and highlight why transition metals are so useful for construction and technology.

最常见的考题之一就是要求你比较过渡金属和第1族金属（碱金属）的物理和化学性质。差异非常显著，这也凸显了为什么过渡金属在建筑和工艺上如此有用。

Property	Transition Metals	Group 1 Metals
Melting and boiling points	High (e.g. iron 1538 °C)	Low (e.g. sodium 98 °C)
Density	High (e.g. iron 7.87 g cm⁻³)	Low (sodium 0.97 g cm⁻³)
Strength and hardness	Strong and hard	Soft, can be cut with a knife
Reactivity with water	Generally unreactive (e.g. iron reacts only with steam; copper does not react)	Very reactive, produce hydrogen and hydroxides
Formation of coloured compounds	Often form coloured compounds	Usually form white or colourless compounds
Catalytic activity	Many are good catalysts	Rarely used as catalysts
Oxidation states	Variable oxidation states (e.g. Fe²⁺ and Fe³⁺)	Only +1 oxidation state

From the table, it is clear that transition metals are much better suited for structural applications, whereas Group 1 metals are too reactive and soft for such uses. You should be able to recall at least three differences in the exam, supported by named examples.

从表中可以清楚地看到，过渡金属更适合用于结构领域，而第1族金属则过于活泼和柔软，不适合这些用途。你应该能在考试中至少回忆出三点不同，并用具体例子加以支持。

5. Variable Oxidation States | 可变化合价

A defining chemical property of transition metals is the ability to form ions with different charges (oxidation states). This is because the energy levels of their 4s and 3d electrons are very close, allowing the atom to lose different numbers of electrons when forming ions.

过渡金属的一个决定性的化学性质是能够形成不同电荷的离子（即具有不同的氧化态）。这是因为它们的4s和3d电子的能级非常接近，使得原子在形成离子时可以失去不同数目的电子。

For iron, the two most common ions are Fe²⁺ (iron(II), where the metal has an oxidation state of +2) and Fe³⁺ (iron(III), oxidation state +3). You will have encountered these in the context of rusting, where iron is first oxidised to Fe²⁺ and then further to Fe³⁺. Copper shows the +1 and +2 states, with Cu²⁺ being the more stable and common ion in aqueous solution. Manganese can exhibit oxidation states from +2 up to +7 in compounds like MnO₄⁻ (manganate(VII)).

对于铁，最常见的两种离子是Fe²⁺（铁(II)，氧化态为+2）和Fe³⁺（铁(III)，氧化态为+3）。你会在铁生锈的过程中接触到它们，铁首先被氧化为Fe²⁺，然后进一步氧化为Fe³⁺。铜表现出+1和+2态，其中Cu²⁺在水溶液中是更稳定、更常见的离子。锰在诸如MnO₄⁻（锰酸根(VII)）等化合物中可以表现出从+2到+7的氧化态。

In the CCEA exam, you may be given the formula of a compound such as FeSO₄ or Fe₂O₃ and asked to work out the oxidation state of the transition metal. Use the rules: oxygen is usually -2, the overall sum of oxidation states equals the charge, and sulfur in sulfate is +6. So in FeSO₄, the sulfate ion has a total charge of -2, therefore iron must be +2.

在CCEA考试中，你可能会被给一个化合物的化学式，如FeSO₄或Fe₂O₃，并被要求计算出过渡金属的氧化态。使用以下规则：氧通常为-2，氧化态的总和等于总电荷，硫酸根中的硫为+6。因此在FeSO₄中，硫酸根离子的总电荷为-2，所以铁必须为+2。

6. Formation of Coloured Compounds | 有色化合物的形成

Most transition metal compounds are brightly coloured, either in the solid state or, more importantly, in aqueous solution. This is because transition metal ions have partially filled d orbitals. When white light shines on a solution containing such ions, some wavelengths of visible light are absorbed to promote an electron from a lower energy d orbital to a higher one (d-d transition). The light that is not absorbed is transmitted or reflected, giving the solution its characteristic colour.

大多数过渡金属化合物，无论在固态下还是更重要的是在水溶液中，都具有鲜艳的颜色。这是因为过渡金属离子含有未完全充满的d轨道。当白光照射到含有这种离子的溶液时，某些波长的可见光被吸收，将一个电子从较低能量的d轨道激发到较高能量的d轨道（d-d跃迁）。未被吸收的光被透射或反射出来，使溶液呈现出特征颜色。

For IGCSE, you do not need to give a full quantum mechanical explanation, but stating that the colour is due to partially filled d orbitals will be enough for full marks if required. More importantly, you must know the specific colours of the most common ions.

对于IGCSE，你不需要给出完整的量子力学解释，但如果需要，说明颜色源于未充满的d轨道就足以拿到满分。更重要的是，你必须记住最常见离子的具体颜色。

Here is a summary of the colours you must learn for CCEA:

以下是CCEA你必需学习的颜色汇总：

Fe²⁺ (iron(II) in aqueous solution) – pale green / 淡绿色
Fe³⁺ (iron(III) in aqueous solution) – yellow or brown (rust colour) / 黄色或棕色（铁锈色）
Cu²⁺ (copper(II) in aqueous solution) – blue / 蓝色
MnO₄⁻ (manganate(VII) ion) – purple / 紫色
Cr³⁺ (chromium(III) in aqueous solution) – green / 绿色
Cr₂O₇²⁻ (dichromate(VI) ion) – orange / 橙色
Co²⁺ (cobalt(II) in aqueous solution) – pink / 粉红色
Ni²⁺ (nickel(II) in aqueous solution) – green / 绿色

Being able to link these colours to the correct ion is a high-frequency exam point. For example, a question might show a blue solution and ask which transition metal ion is present. The answer is Cu²⁺.

能够将这些颜色与正确的离子对应起来是一个高频考点。例如，一道题可能会展示一个蓝色溶液，并问存在哪种过渡金属离子，答案就是Cu²⁺。

7. Catalytic Properties | 催化性质

Transition metals and their compounds are widely used as catalysts in industry and in the laboratory. Their ability to change oxidation states readily allows them to participate in redox cycles that speed up reactions without being used up.

过渡金属及其化合物在工业上和实验室中被广泛用作催化剂。它们能轻易改变氧化态，使它们能够参与氧化还原循环，从而加速反应而自身不被消耗。

One vital example for CCEA is iron, which is used as a catalyst in the Haber process for manufacturing ammonia from nitrogen and hydrogen. The balanced equation for this reaction is N₂(g) + 3H₂(g) ⇌ 2NH₃(g), and the iron catalyst makes the reaction economically viable at moderate temperatures (about 450 °C) and high pressure.

对CCEA至关重要的一个例子是铁，它在哈伯法中用作催化剂，用于从氮气和氢气制造氨。该反应的方程式为N₂(g) + 3H₂(g) ⇌ 2NH₃(g)，铁催化剂使得该反应在中等温度（约450 °C）和高压下具有经济可行性。

Other examples you should know: nickel is used in the hydrogenation of vegetable oils to make margarine, adding hydrogen to carbon-carbon double bonds; platinum and palladium are used in catalytic converters to remove harmful gases from car exhausts; manganese(IV) oxide (MnO₂) catalyses the decomposition of hydrogen peroxide (2H₂O₂ → 2H₂O + O₂); and vanadium(V) oxide (V₂O₅) is a catalyst in the Contact process for making sulfuric acid (though not always required for IGCSE, it is useful context).

你应该知道的其他例子：镍用于植物油的加氢以制造人造黄油，即将氢气加成到碳碳双键；铂和钯用于催化转换器，以去除汽车尾气中的有害气体；二氧化锰（MnO₂）催化过氧化氢的分解（2H₂O₂ → 2H₂O + O₂）；五氧化二钒（V₂O₅）是接触法制造硫酸的催化剂（尽管IGCSE不总是要求，但作为背景知识很有用）。

When answering questions about catalysts, remember to state that a catalyst increases the rate of reaction by providing an alternative pathway with a lower activation energy, and that it remains chemically unchanged at the end of the reaction.

在回答关于催化剂的问题时，记住要说明催化剂通过提供一条活化能较低的替代路径来加快反应速率，并且在反应结束时它本身化学上保持不变。

8. Common Transition Metals and Their Uses | 常见过渡金属及其用途

The CCEA specification expects you to connect the properties of transition metals to their everyday uses. Three metals feature prominently: iron, copper, and chromium.

CCEA大纲希望你将过渡金属的性质与其日常用途联系起来。有三种金属尤为突出：铁、铜和铬。

Iron (Fe) is extracted from its ore in a blast furnace and is the most widely used structural metal. Its high strength and relatively low cost make it ideal for buildings, bridges, and vehicles. However, pure iron is quite soft, so it is often alloyed with carbon and other metals to make steel. Stainless steel, for instance, contains chromium and nickel to prevent rusting.

铁（Fe）在高炉中从矿石里提炼出来，是使用最广泛的结构金属。它的高强度与相对低廉的成本使其成为建筑、桥梁和交通工具的理想材料。然而纯铁相当软，因此通常与碳和其他金属熔炼成钢。例如，不锈钢含有铬和镍，可以防止生锈。

Copper (Cu) is prized for its excellent electrical and thermal conductivity, and its malleability means it can be drawn into thin wires. It is used in electrical cables, plumbing pipes, and roofing. Since copper is relatively unreactive and does not react with water, it is also ideal for hot water tanks and central heating systems.

铜（Cu）因其优良的导电和导热性而备受推崇，其延展性意味着它可以被拉成细线。它用于电缆、水管和屋顶。由于铜相对不活泼且不与水反应，它也是热水水箱和中央供暖系统的理想材料。

Chromium (Cr) is a hard, shiny metal often used as a protective and decorative plating on other metals, such as on car bumpers and bathroom fittings. It resists corrosion because it forms a thin, tough oxide layer on its surface, a process called passivation.

铬（Cr）是一种坚硬、光亮的金属，常作为保护性和装饰性镀层用于其他金属表面，如汽车保险杠和浴室配件。它能抗腐蚀，因为其表面会形成一层薄而牢固的氧化物层，这一过程称为钝化。

You may also be asked about titanium (lightweight, strong, corrosion-resistant, used in aircraft and hip replacements) and manganese (used in alloys to improve hardness). Knowing two or three uses per metal is good exam practice.

你还可能被问到钛（轻质、高强度、抗腐蚀，用于飞机和人工髋关节）和锰（用于合金以提高硬度）。对每种金属掌握两到三种用途是良好的备考方法。

9. Important Transition Metal Ions and Their Colours | 重要过渡金属离子及其颜色

This section reinforces the key colours you must be able to identify or predict. A common exam task is to describe the colour change when one ion is reduced or oxidised. For example, when iron(III) oxide reacts with carbon monoxide in the blast furnace, the reddish-brown Fe³⁺ is reduced to metallic iron, losing its colour. In a laboratory test, adding sodium hydroxide solution to solutions containing transition metal ions produces coloured hydroxide precipitates that are characteristic of each metal ion.

本节强化你必须能够识别或预测的关键颜色。一项常见的考试任务是描述某种离子被还原或氧化时的颜色变化。例如，在鼓风炉中，当氧化铁(III)与一氧化碳反应时，红褐色的Fe³⁺被还原为金属铁，从而失去颜色。在实验室测试中，向含有过渡金属离子的溶液中加入氢氧化钠溶液会产生每种金属离子所特有的有色氢氧化物沉淀。

Ion	Colour of aqueous ion	Precipitate with NaOH
Cu²⁺	Blue	Light blue jelly-like solid (Cu(OH)₂)
Fe²⁺	Pale green	Green precipitate turning brown on standing (Fe(OH)₂ → Fe(OH)₃)
Fe³⁺	Yellow/brown	Brown precipitate (Fe(OH)₃)
Cr³⁺	Green	Grey-green precipitate (Cr(OH)₃), soluble in excess NaOH

Note that Fe²⁺ hydroxide is quickly oxidised by air to Fe³⁺ hydroxide, so the green colour typically changes to brown if left exposed. This is a useful observation to mention. The Cr³⁺ precipitate dissolving in excess NaOH to give a dark green solution is a distinguishing test, but it is not always required at IGCSE – check with your teacher.

注意Fe²⁺氢氧化物在空气中会迅速被氧化为Fe³⁺氢氧化物，因此如果暴露在空气中，绿色通常会转变为棕色。这是一个值得提及的有用观察。Cr³⁺沉淀在过量NaOH中溶解并形成深绿色溶液是一个区分性测试，但在IGCSE阶段不总是要求——请与你的老师确认。

10. Corrosion of Iron and Rusting | 铁的腐蚀与生锈

Rusting is a specific type of corrosion that applies to iron and steel. It is an electrochemical process that requires both water and oxygen to occur. The overall reaction converts iron into hydrated iron(III) oxide, Fe₂O₃·xH₂O, which is a flaky, porous solid that does not protect the iron underneath, so rusting continues until the metal is completely consumed.

生锈是一种专门针对铁和钢的腐蚀类型。它是一个电化学过程，需要水和氧气同时存在才能发生。总反应会将铁转化为水合氧化铁(III)，即Fe₂O₃·xH₂O，这是一种片状、多孔的固体，无法保护内部的铁，因此生锈会持续进行，直至金属完全被消耗。

The chemistry of rusting can be broken down: at anodic sites, iron is oxidised to Fe²⁺ (Fe → Fe²⁺ + 2e⁻); at cathodic sites, oxygen is reduced in the presence of water (O₂ + 2H₂O + 4e⁻ → 4OH⁻). The Fe²⁺ ions then react with hydroxide ions to form Fe(OH)₂, which is further oxidised to Fe(OH)₃, and ultimately dehydrates to form rust. CCEA does not require you to reproduce the full electrochemical mechanism, but you should know that both air and water are essential, and that salt or acid rain accelerates the process.

生锈的化学过程可以分解如下：在阳极区，铁被氧化为Fe²⁺（Fe → Fe²⁺ + 2e⁻）；在阴极区，氧气在水的存在下被还原（O₂ + 2H₂O + 4e⁻ → 4OH⁻）。然后Fe²⁺离子与氢氧根离子反应生成Fe(OH)₂，后者进一步被氧化为Fe(OH)₃，最终脱水形成铁锈。CCEA不要求你复述完整的电化学机理，但你应当知道空气和水都是必要条件，而且盐或酸雨会加速这一过程。

Methods of rust prevention link directly to these requirements. Barrier methods such as painting, oiling, or coating with plastic simply keep water and oxygen away from the iron. Sacrificial protection involves attaching a more reactive metal, such as zinc (galvanising) or magnesium, to the iron. The more reactive metal corrodes preferentially, leaving the iron intact. You should be able to explain why magnesium blocks attached to underground iron pipes stop rusting: magnesium is more reactive and loses electrons in preference to iron.

防锈的方法直接与这些条件相关。屏障法，如涂漆、上油或塑料涂层，直接隔绝了水和氧与铁的接触。牺牲保护法则在铁上附着一种更活泼的金属，如锌（镀锌）或镁。更活泼的金属优先腐蚀，从而保护了铁不受影响。你应该能够解释为什么连接在地下铁管上的镁块可以阻止生锈：镁更活泼，会优先失去电子。

11. Key Exam Tips | 关键考试技巧

When answering CCEA IGCSE questions on transition metals, keep the following points in mind: always support general statements with named examples, for example ‘Transition metals have high melting points, such as iron at 1538 °C’ is stronger than a generic claim. When asked to compare Group 1 and transition metals, use a side-by-side format or a simple table in your mind to ensure you cover density, melting point, strength, reactivity, and ion colour.

在回答CCEA IGCSE关于过渡金属的问题时，请牢记以下几点：始终用具体例子来支持一般性的陈述，例如“过渡金属具有高熔点，例如铁的熔点为1538 °C”比泛泛而谈更有说服力。当被要求比较第1族金属和过渡金属时，可以在脑中采用左右对照的格式或简单表格，确保涵盖密度、熔点、强度、反应性和离子颜色等方面。

Colours are easy marks but easy to confuse. Write down a quick mnemonic: ‘Blue Copper, Green Iron-two, Brown Iron-three, Purple Manganate’ to recall them. For catalysis, recognise the reaction and the catalyst. Do not say a catalyst is ‘used up’ or ‘takes part in the reaction’ without explaining it is regenerated. Always say ‘provides an alternative route with lower activation energy’.

颜色题容易得分但也容易混淆。写下快速记忆口诀：“蓝铜、绿铁二、棕铁三、紫锰根”来回忆它们。对于催化作用，要辨认出反应和催化剂。不要说催化剂被“消耗”或“参与反应”而不解释它会再生。一定要说“提供了一条活化能较低的替代路径”。

Finally, practise writing half equations for oxidation of iron in rusting, and use the correct notation for oxidation states (e.g. iron(II) for Fe²⁺, iron(III) for Fe³⁺). This precise language is what examiners look for in top-band answers.

最后，练习书写铁在生锈过程中氧化的半反应方程式，并使用正确的氧化态表示法（例如，Fe²⁺写作iron(II)，Fe³⁺写作iron(III)）。这种精确的语言是考官在最高分档答案中所寻找的。

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Transition Metals in IGCSE CCEA Chemistry | IGCSE CCEA 化学：过渡金属 考点精讲