📚 Metal Elements | 金属元素
Metals are a large and important group of elements on the periodic table. They are all around us, from the aluminium in drink cans to the iron in bridges and the copper in electrical wires. In this KS3 chemistry article, we will explore the main physical and chemical properties of metals, how they react with oxygen, water and acids, how the reactivity series helps us predict their behaviour, how metals are extracted, and why alloys and rust prevention matter in everyday life.
金属是元素周期表中一大类重要的元素。它们在我们身边随处可见，从饮料罐中的铝，到桥梁中的铁，再到电线中的铜。在这篇 KS3 化学文章中，我们将学习金属的主要物理性质和化学性质、它们与氧气、水和酸的反应、金属活动性顺序如何帮助我们预测金属的行为，以及金属如何被冶炼、合金和防锈在日常生活中有多重要。
1. What Is a Metal Element? | 什么是金属元素
An element is a pure substance made of only one type of atom. Metal elements are found mainly on the left-hand side and in the centre of the periodic table, and most of the elements in the periodic table are metals. A metal element cannot be broken down into anything simpler by chemical means, and every atom in a pure metal sample is the same kind of atom.
元素是由同一种原子组成的纯净物。金属元素主要位于元素周期表的左侧和中部，元素周期表中的大多数元素都是金属。金属元素无法再用化学方法分解成更简单的物质，一块纯净金属中的每一个原子都是同一种原子。
Common examples include iron (Fe), copper (Cu), aluminium (Al), gold (Au), silver (Ag), zinc (Zn), magnesium (Mg), sodium (Na), potassium (K) and calcium (Ca). At room temperature, almost all metals are solids; mercury (Hg) is the only common metal that is a liquid. Bromine is also a liquid at room temperature, but it is a non-metal, so it is not an exception to the rule about metals.
常见的例子包括铁（Fe）、铜（Cu）、铝（Al）、金（Au）、银（Ag）、锌（Zn）、镁（Mg）、钠（Na）、钾（K）和钙（Ca）。在室温下，几乎所有金属都是固体；汞（Hg）是唯一常见的液态金属。溴在室温下也是液体，但它是非金属，所以并不构成对"金属都是固体"这一规律的例外。
A few metals, such as gold, silver and platinum, are found in the Earth as the uncombined element because they are so unreactive. Most other metals are found combined with other elements in compounds called ores. An ore is a rock that contains enough of a metal compound to make it worth extracting the metal.
少数金属，例如金、银和铂，因为它们非常不活泼，所以在自然界中以单质形式存在。其他大多数金属都以化合物的形式与其他元素结合，存在于叫做矿石的岩石中。矿石是指含有足够多的金属化合物、值得把金属提取出来的岩石。
2. Physical Properties of Metals | 金属的物理性质
Metals have a characteristic shiny appearance when they are polished or freshly cut. This property is called metallic lustre. It is why jewellery made from gold or silver looks bright, and why freshly cut sodium looks silvery before it quickly dulls in air.
金属经过抛光或新切开时具有特有的光泽，这种性质叫做金属光泽。这就是为什么金、银首饰看起来光亮，也是为什么新切开的钠表面呈银白色、但很快在空气中变暗的原因。
Metals are excellent conductors of heat and electricity. For example, copper is used in electrical wires because it allows electric current to flow easily, and it is also used in cooking pans because it conducts heat quickly. Silver is an even better conductor than copper, but it is far too expensive to use in ordinary cables.
金属是极好的导热体和导电体。例如，铜被用于电线，因为它能让电流容易通过；铜也被用于锅具，因为它导热很快。银的导电性比铜更好，但价格昂贵得多，因此不用于普通电缆。
Metals are malleable, which means they can be hammered or bent into shape without cracking, and ductile, which means they can be pulled into thin wires. They are usually sonorous, making a ringing sound when struck, which is why metal is used for bells and cymbals.
金属具有延展性（malleable），可以用锤子敲打或弯折成型而不破裂；也具有可塑性/拉丝性（ductile），可以被拉成细丝。金属通常还有"响声"（sonorous），被敲击时会发出清脆的声响，这就是为什么铃铛和铜钹要用金属制作。
Most metals have high melting points and high boiling points, and they are denser than most non-metals. There are, however, important exceptions: sodium and potassium are soft enough to cut with a knife, they are less dense than water, and they have relatively low melting points.
大多数金属有很高的熔点和沸点，密度也大于大多数非金属。不过也有重要的例外：钠和钾软得可以用小刀切开，密度小于水，熔点也相对较低。
| Property 性质 | Meaning 含义 | Example 例子 |
| Lustrous 有光泽 | Shiny when polished 抛光后发亮 | Gold jewellery 金首饰 |
| Conductive 导电导热 | Transfers electricity and heat 能传导电和热 | Copper wires 铜电线 |
| Malleable 有延展性 | Can be hammered flat 能敲打成薄片 | Aluminium foil 铝箔 |
| Ductile 可拉丝 | Can be drawn into wires 能拉成丝 | Copper cable 铜缆 |
| High melting point 高熔点 | Needs strong heating to melt 需要强热才能熔化 | Iron (1538 °C) 铁 |
3. Metals in the Periodic Table | 元素周期表中的金属
The periodic table is arranged in rows called periods and columns called groups. Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell. Metals fill the left and centre of the table, while non-metals are found mainly on the right.
元素周期表按横行（周期）和纵列（族）排列。同族元素的化学性质相似，因为它们最外层电子数相同。金属占据了周期表的左侧和中部，非金属则主要位于右侧。
Group 1 metals are called the alkali metals and include lithium, sodium and potassium. They are soft, have low densities, and react vigorously with water. Reactivity increases as you go down the group, so potassium reacts more violently than sodium, which reacts more violently than lithium.
第 1 族金属叫做碱金属，包括锂、钠和钾。它们质地软、密度低，与水反应剧烈。同族从上到下活动性增强，所以钾比钠反应更剧烈，钠又比锂更剧烈。
Group 2 metals are called the alkaline earth metals and include magnesium and calcium. They are harder and denser than the alkali metals and are less reactive, although calcium still reacts steadily with cold water.
第 2 族金属叫做碱土金属，包括镁和钙。它们比碱金属更硬、密度更大，活动性也更低，不过钙仍然能与冷水稳定反应。
The central block contains the transition metals, such as iron, copper, zinc, silver and gold. Transition metals are generally hard, strong, dense and good conductors, and they are much less reactive than Group 1 metals. They often form coloured compounds, and many of them act as catalysts.
中部区域是过渡金属，例如铁、铜、锌、银和金。过渡金属通常坚硬、强度高、密度大、导电导热性好，而且活动性远低于第 1 族金属。它们常形成有颜色的化合物，其中许多还能作催化剂。
Metalloids, such as silicon, sit on the staircase boundary between metals and non-metals and have properties of both. This is why silicon is used in computer chips while also being a poor conductor at low temperatures.
类金属（半金属），例如硅，位于金属与非金属交界的"阶梯线"上，兼具两者的性质。这就是硅既可以用于电脑芯片、又在低温下导电性很差的原因。
4. Chemical Properties: Metals and Oxygen | 化学性质：金属与氧气
When a metal reacts with oxygen, the metal is oxidised and a metal oxide is formed. This type of reaction is called an oxidation reaction, and it is also a combination reaction because two substances join together to make one new substance. The general word equation is:
金属与氧气反应时，金属被氧化，生成金属氧化物。这类反应叫做氧化反应，同时也是化合反应，因为两种物质结合生成了一种新物质。通用文字方程式是：
metal + oxygen → metal oxide
镁 + 氧气 → 氧化镁
Magnesium burns in air with a brilliant white flame to produce a white powder of magnesium oxide. The reaction is very exothermic, releasing a large amount of energy:
镁在空气中燃烧，发出耀眼的白光，生成白色粉末状的氧化镁。该反应放热明显，会释放大量能量：
2Mg + O₂ → 2MgO
Zinc reacts in a similar way when heated strongly, forming zinc oxide, and iron filings burn with orange sparks to form iron oxide. Copper is much less reactive: it only reacts slowly when heated for a long time, forming a black layer of copper(II) oxide.
锌在强热下发生类似反应，生成氧化锌；铁粉燃烧时产生橙色火花，生成氧化铁。铜的活动性低得多：只有在长时间加热时才缓慢反应，表面生成一层黑色的氧化铜(II)。
2Zn + O₂ → 2ZnO
2Cu + O₂ → 2CuO
Gold and silver do not react with oxygen at all under normal conditions. This is why ancient gold ornaments are still bright after thousands of years, while an iron gate left outdoors soon becomes coated with rust. The more reactive the metal, the faster and more vigorously it reacts with oxygen.
金和银在通常条件下完全不与氧气反应。这就是为什么古代金饰历经千年依然光亮，而放在户外的铁门很快就会生锈。金属越活泼，与氧气反应就越快、越剧烈。
Some metal oxides are amphoteric or basic and dissolve in water to form alkaline solutions. Sodium oxide, for example, dissolves in water to produce sodium hydroxide, a strong alkali. This is one reason why freshly cut sodium is stored under oil rather than in air.
有些金属氧化物溶于水会生成碱性溶液。例如氧化钠溶于水生成氢氧化钠，是一种强碱。这也是新切开的钠要保存在煤油中而不是空气中的原因之一。
5. Metals and Water | 金属与水
Metals react with water in different ways depending on their position in the reactivity series. The most reactive metals react with cold water, less reactive metals need steam, and the least reactive metals do not react at all.
金属与水的反应方式取决于它们在金属活动性顺序中的位置。最活泼的金属与冷水就能反应，活动性较弱的金属需要水蒸气，而活动性最弱的金属则完全不反应。
Potassium, sodium and calcium react with cold water to produce a metal hydroxide and hydrogen gas. Potassium reacts so vigorously that it catches fire and burns with a lilac flame, while calcium fizzes steadily and forms calcium hydroxide, which is only slightly soluble:
钾、钠和钙与冷水反应，生成金属氢氧化物和氢气。钾反应非常剧烈，会着火并发出淡紫色火焰；钙则稳定地冒气泡，生成微溶的氢氧化钙：
2Na + 2H₂O → 2NaOH + H₂
Ca + 2H₂O → Ca(OH)₂ + H₂
Magnesium reacts extremely slowly with cold water, but it reacts quickly with steam to form magnesium oxide and hydrogen. Zinc and iron also react with steam when heated strongly, producing the metal oxide and hydrogen:
镁与冷水反应极其缓慢，但与水蒸气反应很快，生成氧化镁和氢气。锌和铁在强热下也能与水蒸气反应，生成金属氧化物和氢气：
Mg + H₂O → MgO + H₂
Zn + H₂O → ZnO + H₂
Copper, silver and gold do not react with water or steam at all. A useful rule for exams is that the further down the reactivity series a metal is, the more energy you need to make it react with water, and metals below hydrogen in the series do not react with water or dilute acids.
铜、银和金完全不与水或水蒸气反应。考试中一个实用的规律是：金属在活动性顺序中越靠后，让它与水反应所需的能量就越大；位于氢后面的金属既不与水反应，也不与稀酸反应。
6. Metals and Acids | 金属与酸
When a metal reacts with a dilute acid, it produces a salt and hydrogen gas. The salt formed depends on both the metal and the acid used: hydrochloric acid makes chlorides, sulfuric acid makes sulfates, and nitric acid makes nitrates. The general word equation is:
金属与稀酸反应时，生成盐和氢气。生成什么盐取决于金属和所用酸：盐酸生成氯化物，硫酸生成硫酸盐，硝酸生成硝酸盐。通用文字方程式是：
metal + acid → salt + hydrogen
Magnesium reacts very quickly with dilute hydrochloric acid, producing a rapid stream of bubbles. Zinc reacts steadily and iron reacts slowly, producing fewer bubbles over a longer time. Copper does not react with dilute hydrochloric acid at all, because copper is below hydrogen in the reactivity series.
镁与稀盐酸反应非常快，迅速产生大量气泡；锌反应较平稳，铁反应较慢，气泡较少但持续时间更长。铜完全不与稀盐酸反应，因为铜在活动性顺序中位于氢的后面。
Mg + 2HCl → MgCl₂ + H₂
Zn + H₂SO₄ → ZnSO₄ + H₂
Fe + 2HCl → FeCl₂ + H₂
The hydrogen produced can be tested with a lighted splint. If hydrogen is present, the gas burns with a squeaky pop. This is the standard test for hydrogen gas and is often worth a mark in practical questions.
生成的氢气可以用点燃的木条检验。若有氢气，气体会燃烧并发出"爆鸣声"（squeaky pop）。这是氢气标准的检验方法，在实验题中常常是一个得分点。
A metal's reaction with acid can also be used to compare reactivity. If you add equal-sized pieces of different metals to the same acid, the metal that produces bubbles fastest is the most reactive. This is a simple and reliable practical method for building a reactivity series.
金属与酸的反应也可以用来比较活动性。如果把大小相同的不同金属放入同一种酸中，产生气泡最快的金属最活泼。这是构建金属活动性顺序的一种简单而可靠的实验方法。
7. The Reactivity Series | 金属活动性顺序
The reactivity series is a list of metals arranged from most reactive at the top to least reactive at the bottom. Carbon and hydrogen are usually included as non-metal reference points, which helps us decide how a metal is extracted and whether it will react with dilute acid.
金属活动性顺序是把金属按活动性从强到弱排列的清单，最活泼的在最上方，最不活泼的在最下方。通常把碳和氢作为非金属参照物一起列出，这有助于判断金属如何冶炼，以及它是否能与稀酸反应。
| Position 位置 | Metal 金属 | Behaviour 行为 |
| Most reactive 最活泼 | K, Na, Ca | React with cold water 与冷水反应 |
| ↓ | Mg, Al | React with steam 与水蒸气反应 |
| ↓ | C, Zn, Fe | React with acid 与稀酸反应 |
| ↓ | H | Reference point 参照点 |
| Least reactive 最不活泼 | Cu, Ag, Au | Found native, no acid reaction 以单质存在，不与酸反应 |
A common way to remember the series is the sentence "Please Send Cats Monkeys And Zebras In Large Cages Securely Guarded". The first letters match potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver and gold.
记忆活动性顺序的常用方法是口诀（英文首字母法）："Please Send Cats Monkeys And Zebras In Large Cages Securely Guarded"，首字母依次对应钾、钠、钙、镁、铝、锌、铁、铅、铜、银、金。
The reactivity series explains several everyday facts. It explains why gold is found as the pure metal, why iron rusts but copper does not corrode so quickly, and why metals high in the series must be extracted by electrolysis rather than by heating with carbon.
金属活动性顺序解释了不少日常现象：为什么金能以单质形式存在于自然界，为什么铁会生锈而铜腐蚀得慢得多，以及为什么活动性靠前的金属必须用电解法而不是用碳加热来冶炼。
8. Displacement Reactions | 置换反应
A displacement reaction happens when a more reactive metal takes the place of a less reactive metal in a compound. The rule is simple: a more reactive metal will displace a less reactive metal from a solution of its salt, but the opposite never happens.
当较活泼的金属把较不活泼的金属从其化合物中"替换"出来时，就发生了置换反应。规律很简单：较活泼的金属能把较不活泼的金属从其盐溶液中置换出来，反之则永远不会发生。
If a piece of zinc is placed in blue copper(II) sulfate solution, the blue colour gradually fades and a reddish-brown layer of copper forms on the zinc. The solution becomes colourless zinc sulfate:
如果把一块锌放入蓝色的硫酸铜(II)溶液中，蓝色会逐渐褪去，锌表面析出红棕色的铜，溶液变成无色的硫酸锌：
Zn + CuSO₄ → ZnSO₄ + Cu
Iron behaves in the same way, producing pale green iron(II) sulfate and a copper coating. However, if you put a copper coin into zinc sulfate solution, nothing happens, because copper is less reactive than zinc and cannot displace it.
铁的行为类似，生成浅绿色的硫酸亚铁和一层铜。但若把一枚铜币放入硫酸锌溶液中，什么都不会发生，因为铜的活动性低于锌，无法把它置换出来。
Fe + CuSO₄ → FeSO₄ + Cu
Displacement reactions can also occur between a metal and a metal oxide. The thermite reaction between aluminium powder and iron oxide is dramatic and highly exothermic, producing molten iron and a temperature high enough to weld railway tracks:
置换反应也可以发生在金属与金属氧化物之间。铝粉与氧化铁之间的铝热反应非常剧烈且高度放热，生成熔融的铁，温度高到足以焊接铁轨：
2Al + Fe₂O₃ → Al₂O₃ + 2Fe
In all these reactions the more reactive metal loses electrons and is oxidised, while the less reactive metal gains electrons and is reduced. Oxidation is loss, reduction is gain, which gives us the memory aid "OIL RIG".
在所有这些反应中，较活泼的金属失去电子被氧化，较不活泼的金属得到电子被还原。氧化是失电子，还原是得电子，这就是记忆口诀"OIL RIG"（Oxidation Is Loss, Reduction Is Gain）。
9. Extraction of Metals | 金属的冶炼
Metals are extracted from their ores using methods that depend on their reactivity. Metals above carbon in the reactivity series are extracted by electrolysis, while metals below carbon can be extracted by reduction with carbon. This is why the position of a metal in the series has such a big effect on cost and industrial process.
金属从矿石中提取的方法取决于其活动性。活动性高于碳的金属用电解法制取，活动性低于碳的金属可以用碳还原法提取。这就是金属在活动性顺序中的位置会对成本和工业工艺产生巨大影响的原因。
Iron is extracted in a blast furnace. Coke burns in hot air to produce carbon dioxide, which then reacts with more coke to make carbon monoxide. The carbon monoxide reduces the iron oxide ore to molten iron:
铁在高炉中冶炼。焦炭在热空气中燃烧生成二氧化碳，二氧化碳再与更多焦炭反应生成一氧化碳。一氧化碳把氧化铁矿石还原成熔融的铁：
C + O₂ → CO₂
CO₂ + C → 2CO
Fe₂O₃ + 3CO → 2Fe + 3CO₂
Limestone is also added to remove sandy impurities. It decomposes to calcium oxide, which reacts with silicon dioxide to form slag that floats on the molten iron and can be tapped off separately:
高炉中还要加入石灰石以除去砂质杂质。石灰石分解生成氧化钙，氧化钙与二氧化硅反应生成炉渣，炉渣浮在铁水上面，可以单独排出：
CaCO₃ → CaO + CO₂
CaO + SiO₂ → CaSiO₃
Aluminium is extracted by electrolysis of molten aluminium oxide dissolved in cryolite. The process uses a great deal of electricity, which is why aluminium recycling saves
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