* Electron Configuration: Phosphorus has 5 valence electrons, meaning it only needs to gain 3 more to achieve a stable octet. This makes it highly reactive.

* Allotropes: Phosphorus exists in several allotropic forms, with white phosphorus being the most reactive. White phosphorus is highly flammable and reacts readily with oxygen.

* Reactions with Oxygen: Phosphorus readily reacts with oxygen to form phosphorus oxides, releasing a significant amount of heat and light.

* Reactions with Halogens: Phosphorus reacts vigorously with halogens to form phosphorus halides.

* Reactions with Metals: Phosphorus forms phosphides with metals, showcasing its reactive nature.

However, it's important to note:

* Red Phosphorus: Red phosphorus, another allotrope, is much less reactive than white phosphorus. It is used in matches and other applications due to its controlled reactivity.

In summary: Phosphorus is a very reactive non-metal due to its electron configuration, making it prone to forming compounds with other elements. Its reactivity, however, can be controlled by its allotropic forms.