Describe the nature of oxides formed by alkali metals.

Oxides formed by alkali metals are basic in nature and react with water to form alkaline solutions.

Alkali metals, which belong to Group 1 of the periodic table, include lithium, sodium, potassium, rubidium, caesium, and francium. These metals are highly reactive due to their single valence electron, which they readily lose to achieve a stable electron configuration. When alkali metals react with oxygen, they form oxides. These oxides are ionic compounds that contain the metal cation and the oxide anion (O2-).

The nature of these oxides is basic. This means that they react with water to form alkaline solutions. For example, when sodium oxide (Na2O) reacts with water (H2O), it forms sodium hydroxide (NaOH), which is a strong base. This reaction can be represented by the equation: Na2O + H2O → 2NaOH. The resulting solution has a pH greater than 7, indicating its alkaline nature.

The basicity of alkali metal oxides increases down the group. This is due to the increase in atomic size and decrease in ionisation energy, which makes the alkali metals more reactive and their oxides more basic. For instance, potassium oxide (K2O) is more basic than sodium oxide (Na2O).

It's also worth noting that the oxides of alkali metals are white solids at room temperature and have high melting points due to their ionic nature. They are also good conductors of electricity when dissolved in water or melted, due to the movement of ions.

In summary, the oxides formed by alkali metals are basic, reacting with water to form alkaline solutions. Their basicity increases down the group, and they exhibit typical properties of ionic compounds, such as high melting points and electrical conductivity.