Question

Give one example of
a.A triatomic molecule
b.A polyatomic molecule

Answer 1

The diatomic molecule is defined as the molecule which tends to contain two atoms in its composition. Whereas the triatomic molecule is the molecule which tends to contain three atoms in its composition. These three atoms can be of the same or different types.

Complete answer:
In the question we have to write the example of a triatomic molecule. The tri word means three. This means that a triatomic molecule contains three atoms in its composition. So the example of a triatomic molecule which contains two different atoms in it is carbon dioxide $C{{O}_{2}}$. In this molecule we have 1 atom of carbon and two atoms of oxygen. Now the triatomic molecule which contains the same type of three atoms in its composition is ozone ${{O}_{3}}$. In this molecule there are 3 atoms of oxygen. So in a triatomic molecule we should have three atoms, it is not mandatory that it must be of the same or different types.
The polyatomic molecule is the molecule which tends to contain three or more than three atoms in its composition. The atoms in its molecule can be of the same type or different types. So the example of the molecule which contains 5 atoms in the molecule of different types is methane $C{{H}_{4}}$. In methane we have 4 atoms of hydrogen and 1 atom of carbon. The example of the polyatomic molecule which contains 4 atoms of the same type is phosphorus ${{P}_{4}}$.
So the example of a triatomic molecule is $C{{O}_{2}}$ and ${{O}_{3}}$. The example of a polyatomic molecule is $C{{H}_{4}}$ and ${{P}_{4}}$.

Note: The number of atoms present in the molecule defines the atomicity of the molecule. So the atomicity of the triatomic molecule is 3 as it tends to contain three atoms in the molecule. The atomicity of polyatomic molecules varies. For phosphorus it is 4 as it has 4 atoms in its molecule. While for methane it is 5 as it has 5 atoms in its molecule.