* Electronegativity: Chlorine is more electronegative than phosphorus. This means chlorine has a stronger pull on electrons, making it more likely to gain electrons and form negative ions.

* Electron Configuration: Chlorine has one electron short of a full outer shell, making it highly reactive to gain that electron. Phosphorus, on the other hand, has three electrons in its outer shell and tends to lose them to achieve a stable octet.

* Reaction Rates: Chlorine readily reacts with many elements and compounds, while phosphorus reacts more slowly and under specific conditions.

For example, chlorine gas reacts explosively with hydrogen gas in the presence of light, while phosphorus needs specific conditions to react with oxygen.

In summary: Chlorine's higher electronegativity and tendency to gain electrons make it a much more reactive element than phosphorus.