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Writing Chemical Formulae – Rule 3

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Writing chemical formulae – Rule 3

According to the valencies, the net charge on a complete molecule must be balanced.

The third rule of writing chemical formula is governed by valencies of the participating atoms. Let us understand this rule with the help of the water molecule, 𝐻2𝑂.

Structure of water molecule

Structure of water molecule

In 𝐻2𝑂 , the valency of oxygen is 2 and the valency of hydrogen is 1. Hydrogen atom requires 1 electron and oxygen atom requires 2 electrons to achieve the octet state.

This is achieved by sharing of electrons between the hydrogen and oxygen atoms. Hence, 2 hydrogen atoms combine with a single oxygen atom to form a water molecule. Thus, the chemical formula for the water molecule is 𝐻2𝑂.

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  2. Chemical Formulae of Compounds
  3. Concept of Valency – Introduction
  4. The valency of Cl is 1 and not 7 . Give a reason.
  5. Chemical Formulae of Complex Compounds
  6. Chemical Formulae of Complex Compounds – Part 2