Since sulfur is positioned directly under oxygen in the periodic table, one might suspect relatively simple behavior at the atomic level. This is certainly not the case! Indeed, Jerry Donohue, in his authoritative treatise, "The Structures of the Elements," argues, "Of all of the elements, sulfur presents the most confusion and complexity in this respect." Unlike sulfur's near neighbors, such as N, O, Cl, and Br, or P, As, Se, and Te, which in elemental form exist respectively as diatomic molecules or take on polymorphic networks, the four isotopes of sulfur [32S (95.1%), 33S (0.74%), 34S (4.2%), and 36S (0.016%)] combine to form a uniquely large number of allotropic forms (compare Sn, where n = 1–12, 18, and infinity). Of these, only eight have been characterized crystallographically. The most common form, stable at room temperature and atmospheric pressure, is orthorhombic sulfur (S8). Here, eight sulfur atoms bond covalently in crownlike rings. This allotrope, also known as rhombic sulfur, Muthmann's sulfur, and a-S, was among the first substances to be examined crystallographically by William Bragg in 1914.
Phosphorus and sulfur are not diatomic elements. They generally form molecules of P4 and S8 although other forms of these elements also exist. In part this is because they form single bonds rather than the triple and double bonds found in N2 and O2. Phosphorus and sulfur atoms do not have a strong enough pull on electrons to form multiple bonds by themselves.
· 1 decade ago