Sodium is a soft, silver-white metallic element known for its electrical and thermal conductivity. At room temperature sodium is waxlike in composition and is malleable and ductile. Sodium must be derived through chemical means, as it is not found freely in nature.
Sodium has a bright, lustrous appearance when it is freshly cut. When oxidized, sodium's surface tarnishes, darkens and forms a white coat composed of sodium hydroxide and sodium carbonate. As the sixth most abundant element in the Earth's crust, sodium is found in the form of minerals such as feldspar, sodalite and rock salt. Sodium is biologically useful for its roles in regulating blood volume, blood pressure, pH and osmotic equilibrium.