Why sulphur and phosphours does not form many compounds like carbon even though they posses catenation?

Answer 1

Actually, they do form more compounds than most other elements. (Particularly sulfur.)

The reason they don't form as many compounds— and especially large molecules— as carbon is simple: The have a larger atomic radius. Larger radius means longer bonds, lower bond energies and therefore weaker bonds. In large molecules, shear forces or high temperatures can easily break these.

Answer 2

carbon is unique because, when it is bonded to four groups, it has no lone pairs left, and no free low-lying empty orbitals. So it cannot react without going through some kind of unstable intermediate. This is why it is possible to make such a huge variety of carbon compounds without their decomposing, even in cases where decomposition is energetically downhill.

Answer 3

Because Of the Greater Number of protons and electrons when they form co-valent bonds they repel each other and so the attractive force becomes weaker thus it doesn't form too many compounds