Question

Give reasons for the sulphur has greater tendency for catenation than oxygen.

Answer 1

Hint: Catenation is the property of combining with atoms of their own same type. Moving down a group in the periodic table, the number of vacant available orbitals increases. Thus, the tendency to accept more electrons easily also increases. The second shell has only 2s and 2p orbitals while the third shell has empty 3d orbital where it can accommodate electrons.

Complete answer :
First, we will see what is catenation. The catenation may be defined as the property of self-linking. This means the number of atoms of its own type with which it can form stable bonds and can exist. Greater tendency for catenation means it will combine with more numbers of atoms. We have seen that oxygen can exist as ${O_2}$and ${O_3}$. So, it can combine with a maximum of two more atoms. Similarly, sulphur also catenate.
Although sulphur and oxygen belong to the same group, sulphur still has a greater tendency to catenate than oxygen. This is because the oxygen belongs to the second period. So, the filling takes place in 2p orbital while the sulphur belonging to the third period has filling in 3p orbitals. The second shell does not have any d-orbital vacant where filling of electrons can take place. But the third shell has vacant d-orbital where the extra incoming electrons can be accommodated if required.

So, the sulphur has a tendency to form more bonds. Thus, it can easily catenate to oxygen.

Note: It must be noted that the 3d orbital in sulphur is normally vacant. The filling takes place at 3p only. But during catenation, when the more electrons come, they enter the 3d orbital while in oxygen there is no vacant orbital where it can accommodate more electrons and thus, it does not combine with more atoms. So, it shows less catenation.