ga(n = noun.substance) tabun - the first known nerve agent, synthesized by German chemists in 1936; a highly toxic combustible liquid that is soluble in organic solvents and is used as a nerve gas in chemical warfare;
ga(n = noun.substance) atomic number 31, gallium - a rare silvery (usually trivalent) metallic element; brittle at low temperatures but liquid above room temperature; occurs in trace amounts in bauxite and zinc ores;