CHEMICAL REACTIONS

GROUPS OF METALS

Extracted from Chemistry for You (Lawrie Ryan. Published by Nelson Thornes, 2^nd ed. 2001)

►Group 1 The alkali metals

The elements in this first group don’t have many uses as the metals themselves. They are too reactive. However, you will certainly use some of their compounds every day.

Demonstration 5.1 Looking at sodium

Your teacher will show you a piece of sodium.

What is it stored under? Why?

Does the sodium look like a metal?

Your teacher will cut a piece of sodium with a knife.

• How soft is it? What does it look like inside?

• Is this more like a metal now?

Your teacher will warm a small piece of sodium gently on a combustion spoon.

• How easily does sodium melt?

Now you can see why sodium, and the other alkali metals, are unusual metals. They have low melting points and are very soft. For metals, they also have very low densities. You will see in the next experiment that lithium, sodium and potassium float on water!

Look at the table opposite:

• Can you see a pattern going down the group?

• Can you predict the melting point of caesium?

Typical metals have much higher melting points. For example, iron melts at 1540 °C.

Reactions of the alkali metals

The alkali metals are the most reactive group of metals in the Periodic Table. They are too dangerous for you to use in experiments. However, your teacher can show you some reactions of lithium, sodium and potassium.

The Periodic Table is very useful. Its groups make chemistry easier! You only have to learn the reactions of one element in a group. The others are usually similar. For example,

lithium +wateràlithium hydroxide+ hydrogen

(alkaline solution)

Knowing this, we know the equations for the other alkali metals:

sodium + water » sodium hydroxide + hydrogen

• Can you write a word and symbol equation for potassium reacting with water?

Other reactions

The alkali metals react well with non-metals. For example,