Sulphur is less reactive than phosphorus. This is because the P-P bond is weaker than the S-S bond. The bond dissociation energy of P-P bond is 201 kJ/mol, while that of S-S bond is 260 kJ/mol. This means that it takes more energy to break the P-P bond than the S-S bond. As a result, phosphorus is more likely to react with other elements than sulphur.