Though nitrogen gas, †rst isolated in 1772 by the Scottish doctor Daniel Rutherford, makes up over three-quarters of the atmosphere (in dry air, 78.08% to be precise), it is so unreactive that people might question its value. The very strong triple bond in the nitrogen molecule (1.1) makes it very unreactive in a chemical laboratory, though one or two very hot metals like magnesium have enough energy to break the bond and combine. In contrast to the 450°C and 200 times atmospheric pressure needed for a reasonable yield in the Haber process, the nitrogenase enzyme in rhizobium bacteria, found in nodules on the roots of leguminous plants (e.g., pea, bean, vetch, clover, lentil, alfalfa, lupin, peanut) can “†x” nitrogen at ambient temperature and pressure. Some †xation also occurs in thunderstorms when nitrogen and oxygen react to form nitrogen oxides as a žash of lightning supplies the energy.