Chapter 12, Problem 31A

Interpretation Introduction

Interpretation:

The ‘duet’ and ‘octet’ rules are to be explained and their use in describing the arrangement of electrons in a molecule is to be discussed.

Concept introduction:

The ‘duet’ and ‘octet’ rules are rules based on electrons which participate in bond formation.

In molecules, there are various types of bonding. All depends on valence electrons that is the electrons present in outermost shells.

Answer to Problem 31A

The ‘duet’ rule means two electrons in outermost shell.

The ‘octet’ rule means eight electrons in outermost shell.

When ‘duet’ and ‘octet’ rules are followed, the molecules are stable.

In molecules, atoms try to complete its octet (doublet in some cases) and according to it, arrangement of electrons is done.

Explanation of Solution

When a metal reacts with non-metal, ionic bond is formed by complete loss and gain of electrons. When two non-metals react with each other, they are joined by covalent bond.

For example:

  $NaCl$ is ionic compound and $HCl$ is covalent compound.

Sodium has one extra electron in valence shell and chlorine has one less electron from noble gas configuration. So octet rule is followed.

In $HCl$ , hydrogen and chlorine both requires one electron to complete doublet and octet, so they share electrons and octet gets completed

Conclusion

Thus, ‘duet’ and ‘octet’ rules are used in describing the arrangement of electrons in a molecule.