(ii) The oxides of both are much less soluble in water and their hydroxides decompose at high temperature.
(iii) Both react with to form nitrides.
(iv) Neither nor form peroxides or superoxides.
(v) The carbonates of both are covalent in nature. Also, these decompose on heating.
(vi) do not form solid bicarbonates
(vii) Both are soluble in ethanol owing to their covalent nature.
(viii) Both are deliquescent in nature. They crystallize from aqueous solutions as hydrates, for example, and
Q: 8. Explain why alkali and alkaline earth metals cannot be obtained by chemical reduction methods?
In the process of chemical reduction, oxides of metals are reduced using a stronger reducing agent. Alkali metals and alkaline earth metals are among the strongest reducing agents and the reducing agents that are stronger than them are not available. Therefore, they cannot be obtained by chemical reduction of their oxides.
Q: 9. Why are potassium and cesium, rather than lithium used in photoelectric cells?
All the three, lithium, potassium, and cesium, are alkali metals. Still, and are used in the photoelectric cell and no. This is because as compared to and K, is smaller in size and therefore, requires high energy to lose an electron. While on the other hand, and have low ionization energy. Hence, they can easily lose electrons. This property of and is utilized in photoelectric cells.
Q: 10. When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
When an alkali metal is dissolved in liquid ammonia, it results in the formation of a deep blue coloured solution.
The ammoniated electrons absorb energy corresponding to red region of visible light. Therefore, the transmitted light is blue in colour. At a higher concentration (3 M), clusters of metal ions are formed. This causes the solution to attain a copper-bronze colour and a characteristic metallic lustre.