📚 The Group 1 Elements | 第1族元素
The Group 1 elements form the first column of the periodic table. They include lithium, sodium, potassium, rubidium, caesium and francium. These metals look shiny when freshly cut, but they are extremely reactive. In this article, you will learn where they are found, why they behave in similar ways, and how their reactivity changes down the group.
第1族元素位于周期表最左边一列，包括锂、钠、钾、铷、铯和钫。这些金属刚切开时有光泽，但化学性质非常活泼。本文将介绍它们在周期表中的位置、性质相似的原因以及反应性从上到下的变化趋势。
1. Where Are Group 1 Elements? | 第1族元素在哪里？
Group 1 is the first column on the left-hand side of the periodic table. The elements from top to bottom are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs) and francium (Fr). Hydrogen sits at the top of this column in many periodic tables, but hydrogen is a non-metal and is not counted as a Group 1 metal.
第1族是周期表最左侧的一列。从上到下依次是锂（Li）、钠（Na）、钾（K）、铷（Rb）、铯（Cs）和钫（Fr）。许多周期表把氢放在这一列顶部，但氢是非金属，不算作第1族金属。
At KS3 you need to remember the first three elements very well: lithium, sodium and potassium. Rubidium and caesium are more reactive and are usually only shown in demonstrations behind safety screens. Francium is radioactive and extremely rare.
KS3 阶段需要重点记住前三种元素：锂、钠和钾。铷和铯更活泼，通常只在安全屏后的演示中出现。钫具有放射性，极为稀有。
2. Why Are They Called Alkali Metals? | 为什么称它们为碱金属？
Group 1 elements are also called the alkali metals. This name comes from the fact that they react with water to form alkaline solutions. For example, sodium reacts with water to produce sodium hydroxide, which is a strong alkali that turns red litmus paper blue.
第1族元素也称为碱金属。这个名称来源于它们与水反应会生成碱性溶液。例如，钠与水反应生成氢氧化钠，这是一种强碱，能使红色石蕊试纸变蓝。
Because they all have one electron in their outer shell, they form similar compounds and show a clear pattern, or trend, in their properties. This makes Group 1 a good example of how the periodic table groups elements with similar behaviour.
因为它们最外层都有一个电子，所以它们会形成相似的化合物，性质也呈现出明显的规律或趋势。这使得第1族成为周期表将性质相似元素归为一类的很好例子。
3. Physical Properties | 物理性质
Group 1 metals are softer than most metals. Sodium and potassium can be cut with a knife. A freshly cut surface looks shiny, but it quickly tarnishes in air because the metal reacts with oxygen and moisture.
第1族金属比大多数金属软。钠和钾可以用刀切开。刚切开的表面有光泽，但会很快在空气中变暗，因为金属与氧气和水蒸气发生了反应。
They have low densities and low melting points compared with typical metals such as iron. Lithium, sodium and potassium are less dense than water, so they float. The melting points generally decrease down the group: lithium has the highest melting point of the first three, potassium the lowest.
与铁等典型金属相比，它们的密度和熔点都较低。锂、钠和钾的密度比水小，因此能浮在水面上。熔点从上到下总体降低：在前三种元素中，锂的熔点最高，钾最低。
- Lithium melts at about 180 °C.
- Sodium melts at about 98 °C.
- Potassium melts at about 63 °C.
锂的熔点约为 180 °C，钠约为 98 °C，钾约为 63 °C。可以看出，从锂到钾熔点逐渐降低。
4. Electronic Structure | 电子结构
Each Group 1 atom has one electron in its outermost shell. Lithium has the electronic configuration 2,1; sodium has 2,8,1; and potassium has 2,8,8,1. The single outer electron is often called the valence electron.
每个第1族原子的最外层都有一个电子。锂的电子排布是 2,1；钠是 2,8,1；钾是 2,8,8,1。这个唯一的外层电子通常称为价电子。
This one outer electron is the key to their chemistry. To become stable, a Group 1 atom loses this electron and forms a positive ion with a 1+ charge. For example, a sodium atom loses one electron to form Na⁺.
这个外层电子是它们化学性质的关键。为了达到稳定结构，第1族原子会失去这个电子，形成带一个单位正电荷的离子。例如，钠原子失去一个电子形成 Na⁺。
5. Reactivity Trend Down the Group | 反应性自上而下的变化趋势
As you go down Group 1, the elements become more reactive. Lithium is the least reactive of the three common alkali metals, sodium is more reactive, and potassium is even more reactive. Rubidium and caesium are dangerously reactive.
沿第1族从上到下，元素的反应性逐渐增强。在三种常见的碱金属中，锂最不活泼，钠更活泼，钾则更加活泼。铷和铯的活泼程度非常危险。
The reason is that the outer electron is further from the nucleus as the atoms get bigger. The attraction between the nucleus and the outer electron becomes weaker, so the electron is lost more easily. This explains why potassium reacts more vigorously with water than lithium.
原因是随着原子变大，外层电子离原子核更远。原子核对外层电子的吸引力变弱，因此电子更容易失去。这就解释了为什么钾与水的反应比锂更剧烈。
6. Reactions with Water | 与水的反应
All Group 1 metals react with water to produce a metal hydroxide and hydrogen gas. The general word equation is:
所有第1族金属都能与水反应，生成金属氢氧化物和氢气。通用的文字方程式为：
metal + water → metal hydroxide + hydrogen
For sodium, the word equation is:
对于钠，文字方程式为：
sodium + water → sodium hydroxide + hydrogen
During the reaction, the metal moves around on the surface of the water and fizzing is seen as hydrogen gas is released. Enough heat is produced to melt sodium and potassium. Potassium gets so hot that the hydrogen can catch fire, and a lilac flame is often seen.
反应过程中，金属在水面上四处游动，并因放出氢气而产生气泡。反应放出的热量足以熔化钠和钾。钾的反应温度很高，会使氢气燃烧，常能看到淡紫色火焰。
The balanced symbol equation for sodium is:
钠与水的配平化学方程式为：
2Na + 2H₂O → 2NaOH + H₂
For lithium and potassium, replace Na with Li or K in the same pattern.
对于锂和钾，只需按同样的形式将 Na 换成 Li 或 K。
7. Flame Colours | 焰色反应
Group 1 metal compounds give characteristic colours when heated in a flame. Lithium compounds produce a red or crimson flame, sodium compounds give a strong yellow-orange flame, and potassium compounds give a lilac flame. This is one way to identify the metal ion in a sample.
第1族金属的化合物在火焰中加热时会呈现特征颜色。锂化合物产生红色或深红色火焰，钠化合物产生强烈的黄橙色火焰，钾化合物产生淡紫色火焰。这是鉴别样品中金属离子的一种方法。
The yellow sodium flame is very intense and can mask other colours. In the lab, cobalt blue glass is sometimes used to absorb the yellow colour and help show the lilac flame of potassium more clearly.
钠的黄色火焰很强，可能掩盖其他颜色。在实验室中，有时会使用钴蓝色玻璃吸收黄色，以便更清楚地观察到钾的淡紫色火焰。
8. Storage and Safety | 储存与安全
Group 1 metals are far too reactive to be left in air. They are stored under oil to keep oxygen and water vapour away. Lithium is sometimes stored under oil as well, although it is the least reactive of the three common alkali metals.
第1族金属太活泼，不能直接暴露在空气中。它们被保存在油中，以隔绝氧气和水蒸气。锂虽然是三种常见碱金属中最不活泼的，但有时也同样保存在油中。
When handling Group 1 metals, you should use tongs or tweezers, wear safety goggles, and use only very small pieces. Teachers will carry out demonstrations behind a safety screen because the reactions can produce heat, alkalis and flammable hydrogen gas.
处理第1族金属时，应使用镊子或钳子，佩戴护目镜，并且只使用很小的颗粒。教师会在安全屏后进行演示，因为反应会产生热量、强碱和易燃的氢气。
9. Compounds of Group 1 | 第1族元素的化合物
Group 1 metals react with non-metals to form ionic compounds. For example, sodium reacts with chlorine to form sodium chloride, NaCl, which is common table salt. Potassium reacts with chlorine to form potassium chloride, KCl.
第1族金属与非金属反应生成离子化合物。例如，钠与氯反应生成氯化钠（NaCl），也就是常见的食盐。钾与氯反应生成氯化钾（KCl）。
Most Group 1 compounds are white or colourless solids. They usually dissolve well in water. Their solutions conduct electricity because the ions are free to move. This links to the idea that Group 1 elements form positive ions in their compounds.
大多数第1族化合物是白色或无色的固体，通常易溶于水。它们的水溶液能够导电，因为离子可以自由移动。这与第1族
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