A Guide to the Alkali Metals
Explore the highly reactive, soft metals of Group 1 on the periodic table.
What Are Alkali Metals?
The alkali metals are the elements located in Group 1 of the periodic table. This group includes Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr). Hydrogen is also in Group 1 but is typically excluded due to its unique, non-metallic properties.
These metals are famous for their extreme reactivity, which increases as you go down the group. They are so reactive that they are never found in their pure form in nature and must be stored in oil to prevent them from reacting with air and water.
Key Characteristic: One Valence Electron
The defining feature of an alkali metal is its electron configuration. Every element in this group has only one electron in its outermost shell (valence shell).
- This single electron is very loosely held and is easily lost.
- By losing this one electron, the atom achieves a stable, full outer shell, like a noble gas.
This eagerness to donate an electron is what makes the alkali metals the most reactive group of metals on the periodic table. They readily form a +1 ion (e.g., Na⁺, K⁺).
Location on the Periodic Table
The alkali metals occupy the first column on the far-left of the periodic table, Group 1 (excluding Hydrogen).
Properties and Uses of Alkali Metals
Alkali metals share several distinct physical and chemical properties.
| Property | Description |
|---|---|
| Reactivity | Extremely reactive; react violently with water to produce hydrogen gas and an alkaline solution. Reactivity increases down the group. |
| Hardness | Very soft, can be easily cut with a knife. Hardness decreases down the group. |
| Appearance | Silvery-white metals with a shiny luster that quickly tarnishes in air. |
| Density | Have low densities. Lithium, Sodium, and Potassium are less dense than water and will float. |
| Melting/Boiling Points | Have low melting and boiling points compared to other metals. These points decrease down the group. |
| Common Uses | Lithium (Li): Rechargeable batteries. Sodium (Na): Table salt (NaCl), streetlights, biological nerve function. Potassium (K): Fertilizers, biological nerve function. |
Key Takeaways
- Alkali metals are in Group 1 of the periodic table.
- They are defined by having a single valence electron, which they readily lose to form a +1 ion.
- This makes them the most reactive group of metals.
- They are soft, have low densities, and low melting points.
- They are never found in their pure form in nature due to their high reactivity.
Frequently Asked Questions
Why are they called alkali metals?
They are called alkali metals because when they react with water, they form strong alkalis (bases), such as sodium hydroxide (NaOH). The word "alkali" is derived from the Arabic word al qaly, meaning "the ashes," as early chemists isolated compounds like potassium carbonate from wood ashes.
What makes alkali metals so reactive?
Their high reactivity is due to their electron configuration. Each alkali metal has only one electron in its outermost shell. They can achieve a very stable electron configuration (like a noble gas) by losing this single electron, which they do very readily in chemical reactions.
Which alkali metal is the most reactive?
Reactivity increases as you go down the group. Therefore, Francium (Fr) is the most reactive alkali metal. However, since Francium is extremely rare and radioactive, Cesium (Cs) is the most reactive stable alkali metal that can be observed in a typical lab setting.
Why are alkali metals so soft?
Their softness is due to weak metallic bonding. With only one valence electron per atom to contribute to the "sea of electrons" that holds the metal together, the cohesive forces are weaker compared to other metals, allowing the atoms to be moved apart easily with a knife.