Placing a small piece of element from Group 1A in water results in increasingly rapid and violently spectacular reactions as we progress from lithium down to cesium.

What information in this chapter makes this behavior understandable?

Hello, there are two properties of alkaline metals that make them have that behavior:

1. They have large electrode potential which allows them to displace the hydrogen in the water.

2. They released energy when the hydrogen is displaced is big enough to make it ignite.

Now, the reaction is more violent when increasing the period of the alkaline metal because the higher the period (atomic radius as well) the higher the electrode potential which increases the released energy.

Best regards.