Valency of oxygen is generally two whereas Sulphur shows valency of two, four and six. Explain.

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Hint:. In oxygen, there are no vacant orbitals for the excitation of electrons whereas on the other hand, such orbitals are present in case of Sulphur where it can excite its electrons. Now on this basis, you can answer the given statement.

Complete step by step answer:
- Now let’s first of all discuss the oxygen and Sulphur. Both oxygen and Sulphur are the non-metals and are present in the 16th group of the periodic table.
- Oxygen has the atomic number as 8 and mass number as 16. The general electronic configuration of oxygen atom is as: $1{{s}^{2}}2{{s}^{2}}{{p}^{4}}$ and requires two electrons to complete its octet.
- On the other hand, Sulphur has the atomic number as 16 and mass number as 32. The general electronic configuration of Sulphur atom is as: $1{{s}^{2}}2{{s}^{2}}{{p}^{6}}3{{s}^{2}}{{p}^{4}}$ and requires two electrons to complete its octet.

Now considering the statement;
- Oxygen due to absence of the d-orbitals cannot expand its valency whereas on the other hand, in Sulphur due to the availability of vacant d-0ortbitals, it can expand its valency by exciting or promoting the electrons in the empty d-orbitals.
- Thus, that’s why the valency of oxygen is generally two whereas Sulphur shows valency of two, four and six.

Note: Valency of an atom may be defined as the tendency of the atom to ,lose or gain electrons to complete their octet or to acquire the stable electronic configuration of the nearest noble gas. For metals, it is always equal to the number of electrons present in the outermost shell of the metal and for non-metals, it is always equal to the eight minus the number of electrons present in the outermost valence shell.