Question

Why are they called alkali metals?

Answer 1

The elements which are present in group I of the periodic table are known as alkali metals. They are called so because of their particular chemical property.

Complete answer:
The group I of the periodic table contains metals which are known as the alkali metals. They have a single electron in their outermost shell and by removing this electron they can attain a noble gas configuration which is highly stable. Hence they are very reactive in nature.
The alkali metals are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr).
The alkali metals react vigorously with water forming soluble hydroxides which are called alkalis. This is the reason why these metals are called alkali metals. Let us see some of the examples of alkali formation.

& \underset{\text{Alkali Metal}}{\mathop{2Na}}\,+2{{H}_{2}}O\to \underset{\text{Alkali}}{\mathop{2NaOH}}\,+{{H}_{2}} \\\ & \underset{\text{Alkali Metal}}{\mathop{2K}}\,+2{{H}_{2}}O\to \underset{\text{Alkali}}{\mathop{2KOH}}\,+{{H}_{2}} \\\ \end{aligned}$$ Alkalis are considered to be very strong bases and they are caustic in nature. Alkalis react with acids to form water and salt and this reaction is known as neutralization reaction. An example of this reaction is given below: $$\underset{\text{Alkali}}{\mathop{NaOH}}\,+\underset{\text{Acid}}{\mathop{HCl}}\,\to \underset{\text{Salt}}{\mathop{NaCl}}\,+\underset{\text{Water}}{\mathop{{{H}_{2}}O}}\,$$ Among all the alkali metals, francium (Fr) is radioactive and most reactive. The least reactive alkali metal is lithium (Li). Thus, the reactivity increases down the group. Hence, alkali metals are called so because of their ability to form alkalis on reacting with water. **Note:** Alkali metals are highly reactive and they should be handled with proper protection. They can react with the moisture and oxygen present in the air. This is the reason sodium, an alkali metal is stored in kerosene.