Reactive nonmetals
Reactive non-metals gather the light elements essential to life: H, C, N, O, P, S, Se. They account for all of organic chemistry and a large share of common inorganic chemistry.
These are the fundamental building blocks of biochemistry: hydrogen and oxygen make up water; carbon, hydrogen, nitrogen and oxygen constitute proteins, carbohydrates and lipids; phosphorus and sulfur enter DNA, ATP and sulfur-containing amino acids.
Their high electronegativity and small atomic radius (especially for H, C, N, O) enable stable multiple covalent bonds — the basis of the molecular diversity of life.
In industrial chemistry, they are produced on enormous scales: H₂ for ammonia synthesis, O₂ for metallurgy and respiratory support, N₂ as an inert gas, S for sulfuric acid, P for fertilisers.