Group 1 - The Alkali Metals | The Periodic Table | Properties of Matter | Chemistry | FuseSchool

Summary

This lesson covers the alkali metals in Group 1 of the periodic table, including lithium, sodium, potassium, rubidium, cesium, and francium. These metals all have one electron in their valence shell, making them highly reactive. The video demonstrates practical reactions of these metals with water, showing how they become increasingly softer and more reactive as you move down the group. Key observations include their reaction with water to produce hydrogen gas and their corresponding metal hydroxide. The summary also explains trends in density, melting, and boiling points as you move down the group.

Takeaways

• 😀 Alkaline metals are in Group 1 of the periodic table, including lithium, sodium, potassium, rubidium, cesium, and francium.
• 😀 These metals have one electron in their valence shell, which they can lose to form a +1 charged ion.
• 😀 Alkali metals react with oxygen and water vapor in air to form oxides and need to be stored in oil to prevent these reactions.
• 😀 A practical demonstration with lithium, sodium, and potassium shows their reactivity with water, forming alkaline solutions.
• 😀 Lithium reacts with water to form hydrogen gas and lithium hydroxide, and it produces a blue or purple solution when universal indicator is added.
• 😀 Sodium is softer than lithium and reacts more vigorously with water, producing hydrogen gas and sodium hydroxide.
• 😀 Potassium is softer than sodium and reacts even more vigorously with water, producing hydrogen gas and potassium hydroxide, along with a lilac flame.
• 😀 Potassium's reaction can cause it to burn with a lilac flame and may create a popping sound due to hydrogen combustion.
• 😀 All alkali metals float on water, unlike alkaline earth metals (Group 2), which sink when they react with water.
• 😀 Moving down Group 1, alkali metals become softer, more reactive, and have increasing density, while their melting and boiling points decrease.

Q & A

What are alkali metals, and which elements are classified as alkali metals?

Alkali metals are the elements found in Group 1 of the periodic table. These include lithium, sodium, potassium, rubidium, cesium, and francium.

What characteristic do all alkali metals share regarding their electron configuration?

All alkali metals have one electron in their valence shell, which they can lose to form a positive ion with a +1 charge.

Why are alkali metals stored in oil?

Alkali metals are stored in oil because they react readily with oxygen and water vapor in the air, forming a layer of oxides.

What happens when lithium is dropped in water?

When lithium is dropped into water, it floats, fizzes, and slowly disappears, producing hydrogen gas and lithium hydroxide. The solution turns blue or purple, indicating it is alkaline.

How does sodium react differently from lithium with water?

Sodium is softer than lithium, making it easier to cut. It reacts more vigorously with water than lithium, producing hydrogen gas and sodium hydroxide, and also turns the solution blue or purple.

What is observed when potassium reacts with water?

Potassium is softer than sodium and reacts more vigorously with water. It burns with a lilac flame, and a small popping noise can be heard due to the combustion of hydrogen gas.

What are some key trends in the reactivity of alkali metals as you move down the group?

As you move down Group 1, alkali metals become increasingly softer and more reactive with water. Their density increases, but their melting and boiling points decrease.

Why do alkali metals float on water, while alkaline earth metals sink?

Alkali metals float on water because they are less dense than water. In contrast, alkaline earth metals (Group 2) are denser and sink when they react with water.

What is an important observation when potassium reacts with water?

An important observation when potassium reacts with water is that it burns with a lilac flame, which is a distinctive characteristic of its reaction.

What are the properties of francium, and why is it less studied?

Francium is radioactive and very rare in nature, which makes it difficult to study. It is expected to be much softer and more reactive than cesium.