Reactions of the Period 3 elements

Authors Avatar

Reactions of the Period 3 elements

In this essay, I would like to describe the reactions of the Period 3 elements from sodium to argon with water, oxygen and chlorine.

Reactions with water

For sodium, sodium has a very exothermic reaction with cold water producing hydrogen and a colourless solution of sodium hydroxide.

For magnesium, magnesium has a very slight reaction with cold water, but burns in steam.

A very clean coil of magnesium dropped into cold water eventually gets covered in small bubbles of hydrogen which float it to the surface. Magnesium hydroxide is formed as a very thin layer on the magnesium and this tends to stop the reaction.

Magnesium burns in steam with its typical white flame to produce white magnesium oxide and hydrogen.

If you are heating the magnesium in a glass tube, the magnesium also reacts with the glass. That leaves dark grey products (including silicon and perhaps boron from the glass) as well as the white magnesium oxide. The oxide is also produced on heating in steam. Hydroxides are only ever produced using liquid water.

For aluminium, aluminium powder heated in steam produces hydrogen and aluminium oxide. The reaction is relatively slow because of the existing strong aluminium oxide layer on the metal, and the build-up of even more oxide during the reaction.

Join now!

For silicon, there is a fair amount of disagreement in the books and on the web about what silicon does with water or steam. The truth seems to depend on the precise form of silicon you are using.

The common shiny grey lumps of silicon with a rather metal-like appearance are fairly unreactive. Most sources suggest that this form of silicon will react with steam at red heat to produce silicon dioxide and hydrogen.

But it is also possible to make much more reactive forms of silicon which will react with cold water to give the same products.


This is a preview of the whole essay