Question

The elements of group are called alkali metals because:
A. their oxides form acidic solutions on treating with water.
B. their peroxides form alkaline solutions on treating with water.
C. their oxides and hydroxides form alkaline solutions for treating with water.
D. their hydroxides form acidic solutions on treating with water.

Answer 1

Hint:
The alkali metals are the elements of the first group in the periodic table. They have one valence electron in their outermost energy level. They are found in nature bonded with other atoms because they are so reactive. The alkali metals are Lithium, sodium, potassium, rubidium, cesium, and francium.

Complete step by step solution
Alkali metal means a metal whose hydroxide is a water soluble base. The term earth stands for the oxide mineral of an element. So, an alkaline earth metal means a metal whose oxide has similar properties as that of an alkali. If a metal oxide has the properties of an alkali, the hydroxide of the metal should be behaving like an alkali. Alkali metals react with oxygen in the atmosphere and from normal oxides. All the elements present in the group first form normal oxides and excluding lithium all metals who are placed in other groups form peroxide when they are heated in air. Excluding lithium and sodium, all different metals form superoxides. The oxides are basic in nature and when dissolved in water produce alkaline solutions.

Therefore, the correct answer is C.

Note:
Alkali metals have similar chemical properties but different reactivity because they are in the same group. This suggests that they will have the same number of valence electrons in their outermost shell.