Question

Statement-1: An atom having a valency of two can combine with two other atoms, each having a valency of one.

Statement-2: The valency of carbon in carbon dioxide $\left(C{O}_2\right)$ is two.

• A. Only statement 1 is true.
• B. Both statements are false.
• C. Both statements are true.
• D. Only statement 2 is false.

Answer 1

The correct option is A Only statement 1 is true.

The combining capacity of an element is known as its valency. So, an element having a valency of 2 can combine with two atoms of an element having a valency of 1.

The formula of carbon dioxide $\left(C{O}_2\right)$ is written from a short-cut method as shown below.
Symbol: C O
$\searrow \swarrow$
Valency: 4 2

From the above method, the formula obtained for carbon dioxide is $C_2{O}_4$. This formula is simplified taking whole no. ratio of valencies and written as $C{O}_2$. Hence, the valency of carbon is always 4.

So, the valency of an element cannot always be derived from its compounds.