Group 14: the carbon group

Four outer electrons: ns² np²

Each configuration ends in ns² np², as in carbon ([He] 2s² 2p²) and silicon ([Ne] 3s² 3p²). Four electrons is halfway to a full octet, so gaining or losing all four is hard. Instead, carbon and silicon share them, forming four covalent bonds, as in methane (CH₄) and silicon dioxide (SiO₂). Carbon’s oxidation states run from −4 in methane to +4 in carbon dioxide.

Down the group the +2 state becomes more important. Tin forms both +2 and +4 compounds, and lead is most stable as Pb²⁺.

Trends down the group

Density rises from 2.267 g/cm³ for carbon (as graphite) to 5.323 g/cm³ for germanium and 11.34 g/cm³ for lead. First ionization energy falls from 11.26 eV for carbon to 7.344 eV for tin, so the heavier atoms give up electrons more easily and behave like metals. Melting points drop from 1687 K for silicon to 1211.4 K for germanium and 505.08 K for tin, while lead melts at 600.61 K.

Where you meet group 14

Carbon is the backbone of every living thing, of fuels and of plastics, because its atoms link into long chains and rings. Silicon, refined from sand, is the material of computer chips and solar cells, and silicates make up most rocks. Germanium helps carry light in fiber-optic cables, tin coats steel cans and is the main metal in solder, and lead is still used in car batteries and radiation shields.

Surprises in the column

Germanium was predicted before it was found. In 1871 Mendeleev left a gap below silicon and described a missing eka-silicon with a density of about 5.5 g/cm³; germanium, discovered in 1886, came in at 5.323 g/cm³. Tin has its own surprise: below about 13 °C, shiny white tin can slowly crumble into brittle gray tin. Flerovium (114) has been made only a few atoms at a time, so its properties are predicted, not measured.