# What is one property of phosphorous?

Its $\text{atomic number}$ is $15$. Its atomic mass is $31.0 \cdot g \cdot m o {l}^{-} 1$. The element occurs as a couple of allotropes, $\text{red phosphorus}$, which is oligomeric...and the more reactive $\text{white phosphorus}$, which is molecular, and occurs as ${P}_{4}$ tetrahedra.