Question

Why are the elements lithium, sodium and potassium called alkali metals?

• A. Because they reacts with water to form alkali
• B. Because they form acidic oxides
• C. Because they are present in first group
• D. Because they are less reactive in nature

Answer 1

The correct option is A

Because they reacts with water to form alkali

Explanation for the correct option:

(A) Because they react with water to form alkali:

• The valence electron of Lithium, Sodium, and Potassium is same, i.e.$1$. Hence, they belong to the same group.
• All of these elements undergo a chemical reaction with water and results in the formation of an alkali. Therefore, they are known as alkali metals.
• Consider the following equation:
• $2\mathrm{Li}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{LiOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

Hence, (A) is the correct option.

Explanation for the incorrect options:

(B) Because they form acidic oxides:

• Alkali metals form basic oxides when dissolved in water.

(C) Because they are present in the first group:

• Hydrogen (H) is also present in group $1$, and has one electron in its valence shell. However, it is not classified as an alkali metal.

(D) Because they are less reactive in nature:

• Alkali metals are highly reactive in nature.

Therefore the correct option is (A) Because they react with water to form alkali. The given elements are known as alkali metals because they react with water to form alkali.