Question

I don't understand using valency of an element in writing chemical formula

Answer 1

Answer:

eg: calcium and chlorine

Explanation:

ca valency is +2

cl valency is -1

Now

ca cl

(+2) (-1)

cross their valencies with each other

calcium get -1 and cl get -2 valency.

So formula becomes cacl2

Answer 2

Explanation :-

• First of all, let us know what is valency of an element. It is the "combining power" of an element.
• Let us know how we can use valency in writing chemical formulae.
• For example, consider Mg⁺² and OH⁻

• First, write down the ion and its valency(note that, valency has no signs) below it

                  Mg                      OH

                  2                           1

• Now, according to criss cross method, 1 will be applicable to Mg and 2 will be applicable for OH

      So, the chemical formula will be Mg(OH)₂

• If both the ions have same valency, then the valencies get cancelled

      Ex :   Consider Mg⁺² and O⁻²

  → As both have same valencies, the chemical formula will be MgO

   (Refer to the attachment for better understanding)

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→ Sathvik :)