Occurrence

Molecular nitrogen, $N_2$, makes up about 78% of the atmosphere by volume, making it by far the largest reservoir of the element. Within the earth's crust it turns up chiefly as two mineral nitrates — sodium nitrate, $NaNO_3$, historically called Chile saltpetre, and potassium nitrate, commonly known as Indian saltpetre. Living systems also store nitrogen, since it is a building block of the proteins present in every plant and animal.

Phosphorus, by contrast, is locked up mainly in rock-forming minerals of the apatite family, with the general formula $Ca_9(PO_4)_6.CaX_2$ where $X$ can be $F$, $Cl$ or $OH$ — fluorapatite, $Ca_9(PO_4)_6.CaF_2$, is a familiar example, and these apatites form the bulk of natural phosphate rock. Like nitrogen, phosphorus is biologically indispensable: it is a structural part of bone, occurs inside living cells, and appears as phosphoproteins in foods such as milk and eggs.

Arsenic, antimony and bismuth occur predominantly as sulphide minerals rather than as nitrates or phosphates. The final member of the group, moscovium, does not occur naturally at all — it is an artificially synthesised radioactive element, symbol $Mc$, atomic number 115, atomic mass 289, with electronic configuration $[Rn]5f^{14}6d^{10}7s^27p^3$. Because it survives for only a very short time and can be made in only minute quantities, its chemical behaviour has not yet been properly characterised. …