Chem230 Wiki

Trend 6.9 of the Oxygen Group (Group VIA) Trends says that the tendency towards catenation reaches a maximum at sulfur, which forms a wide range of ring and chain compounds, e.g. Sn, XSnX, [O3S(Sn)SO3]2-, and S82+.


Catenation is the tendency for covalent bonds to form between atoms of a given element (e.g. O—O). The trend of catenation deals with E-E bond stability.

The order of E-E stability in Group VIA is:

O < S > Se > Te

with Sulfur having the strongest tendency for catenation. This is seen in the elemental S8 form of sulfur, for example.


The catenation trend is because of size in 2 ways:

A) The decrease of E-E stability from S > Se > Te can be explained by the increasing size of the atoms as you go down the column. The increased bond length causes a decreased bond strength. As you go down the column, the E-E bond strength weakens and becomes less stable, so there is less of a tendency toward catenation.

B) The increase of E-E stability from O to S can be explained by lone pair lone pair repulsions. While O-O is a much shorter bond because of Oxygen's much smaller size, because O-O is so short the lone pairs on each oxygen atom repulse each other significantly and decrease the bond strength. In S-S, the bond length is longer and the lone pair repulsions do not significantly effect the bond strength.