Question

Why does phosphorus have a low melting point?

Answer 1

As a solid absorbs kinetic energy, its particles vibrate more rapidly as it heats up. Eventually, the solid structure's particle order begins to break down, and the solid begins to melt. The temperature at which a solid transforms into a liquid is known as the melting point.

Complete answer:
Phosphorus is a chemical element with atomic number 15 and the symbol P. Phosphorus exists in two primary forms: white phosphorus and red phosphorus, although it is never found as a free element on Earth due to its strong reactivity. It has a concentration of around one gramme per kilogramme in the Earth's crust. Phosphate is the most common form of phosphorus in minerals. Phosphorus is a vital element for life since it is found in phosphates, which are molecules that contain the phosphate ion.
We're dealing with distinct ${{P}_{4}}$ tetrahedra when it comes to white phosphorus. Furthermore, molecular species should be somewhat volatile or low-melting, with little intermolecular interaction. On the other hand, elemental phosphorus comes in a variety of non-molecular allotropes with greater melting and boiling temperatures.
Phosphorus comes in a variety of allotropes, each with its own set of characteristics. White phosphorus and red phosphorus are the two most frequent allotropes. ${{P}_{4}}$ molecule structure as established by gas electron diffraction.
White phosphorus, abbreviated as WP, is the most important type of elemental phosphorus in terms of uses and chemical literature. It's a soft, waxy substance made up of tetrahedral ${{P}_{4}}$ molecules with a single link connecting each atom to the other three.
This ${{P}_{4}}$ tetrahedron may also be found in liquid and gaseous phosphorus until it reaches $800\text{ }{}^\circ C$($1,470\text{ }{}^\circ F$), at which point it begins to decompose into ${{P}_{2}}$ molecules. There are two crystalline forms of white phosphorus: $\alpha$ and $\beta$. The $\alpha$- form, which is more common, is stable at ambient temperature and has a cubic crystal structure; however, at 195.2 K $(78.0\text{ }{}^\circ C)$, it changes into the $\beta$ -form, which has a hexagonal crystal structure. The relative orientations of the component ${{P}_{4}}$ tetrahedra differ between these types.

Note:
The least stable, most reactive, most volatile, least dense, and most poisonous of the allotropes is white phosphorus. The colour of phosphorus changes from white to red over time. Because light and heat hasten this transition, samples of white phosphorus nearly always contain some red phosphorus and look yellow as a result. As a result, aged or otherwise impure white phosphorus (e.gweapons-grade, not lab-grade WP) is referred to as yellow phosphorus.