The elements that build life rather than conduct electricity
Hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium. They are poor conductors, brittle when solid, and utterly essential: better than 99% of every living thing by mass is made of just four of them.
Highlighted in the periodic table
Every member
What defines them
High electronegativity and high ionisation energy mean nonmetals pull electrons toward themselves. With metals they form ionic compounds; with each other they share, producing the covalent molecules that biology is built from.
Without a sea of delocalised electrons there is nothing to conduct heat or electricity and nothing to let atoms slide past one another. Nonmetals are therefore insulating, brittle and often gaseous.
Small nonmetal atoms form strong double and triple bonds — which is why N₂ is so unreactive and why CO₂ is a gas while SiO₂ is rock. Many take several structural forms: carbon as diamond, graphite and graphene; phosphorus as white, red and black.
Periodic trends
Electronegativity and ionisation energy rise toward the top right of the table, peaking at fluorine and oxygen. Melting points vary wildly because structure, not bonding strength alone, decides them: carbon sublimes above 3,800 K while nitrogen boils at 77 K.
In the world
Ammonia synthesis, oil refining, rocket fuel and — increasingly — energy storage.
Steel, plastics, fuels, fibres and every organic molecule in existence. As diamond it cuts; as graphite it lubricates.
Fertiliser via the Haber–Bosch process, which feeds roughly half the world's population. Liquid nitrogen is the workhorse cryogen.
Steelmaking, medicine, water treatment, and respiration. It is the most abundant element in the crust and in your body by mass.
Fertiliser, detergents, matches — and the backbone of DNA and of ATP, the molecule that powers every cell.
Sulfuric acid, the highest-tonnage industrial chemical in the world, plus vulcanised rubber and fungicides.
Handling
Wildly variable. Oxygen and nitrogen are safe to breathe in the right proportions and dangerous in the wrong ones — pure oxygen makes fires uncontrollable, and pure nitrogen asphyxiates without warning. White phosphorus ignites in air and causes deep burns. Hydrogen sulfide is as toxic as cyanide and disables your sense of smell at dangerous concentrations.
Worth knowing
Common questions
Halogens and noble gases are nonmetals — they are simply the two families distinctive enough to be named separately. What is left over gets called "other nonmetals" or "reactive nonmetals": hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium.
Conduction needs electrons that are free to move through the material. In a metal, outer electrons are delocalised across the whole lattice. In a nonmetal they are locked into specific covalent bonds or lone pairs. Graphite is the famous exception: its layered structure leaves one electron per carbon delocalised across each sheet, so it conducts along the layers.
Six make up about 99% of your body: oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus — four of them nonmetals. Sulfur and selenium are required in smaller amounts, sulfur in two amino acids and selenium in the enzymes that mop up oxidative damage.
Keep going