Question

HOW CAN YOU WRITE A FORMULA FROM THE KNOWLEDGE OF VALENCY GIVE AN EXAMPLE IN SUPPORT OF YOUR ANSWER​

Answer 1

$\rule{200}4$

$\large\underline{\underline{\sf \red{Complete\: Question:-}}}$

✤ How can you write a formula of a compound from the knowledge of valency ? Give an example in support of your answer.

$\large\underline{\underline{\sf \red{Answer:-}}}$

We know that valency is the combining capicity of an element . We can find the valency of a element if we know it's atomic number . And we can find the molecular formula of a compound by the knowledge of valency by cross Multiplying their valencies with elements .A molecular formula uses chemical symbols and subscripts to indicate the exact numbers of different atoms in a molecule or compound.

$\bf For\: example$ - If we want to know the molecular formula of Calcium oxide . Calcium oxide is made up of Calcium and Oxygen .Then we know that the valency of Calcium is 2 and that of oxygen is also 2 . Then ,

$\boxed{\setlength{\unitlength}{1 cm}\begin{picture}(5,5)\put(1,1){\vector(1,1){3}}\put(4,1){\vector( - 1,1){3}}\put(1,0.6){2}\put(4,0.6){2}\put(0.8,4){ \tt Ca }\put(4.1,4){ \tt O }\end{picture}}$

( Can refer to attachment also )

By changing their valencies , the formula of compound will be $\rm Ca_2O_2$ . Since 2 is common in both , on cancelling the formula becomes $\bf\green{CaO}$.

$\boxed{\red{\sf\purple{\leadsto}\: Molecular\: formula\:of\: Calcium\:oxide\:\purple{\dashrightarrow}CaO}}$

$\rule{200}4$