Silicon tetrafluoride molecule. Chemist holding a molecular ball-and-stick model of the tetrahedral structure of silicon tetrafluoride (SiF4) also known as tetrafluorosilane. This poisonous, corrosive gas is used in the production of other fluorosilicates and by the military for generating smoke screens. The atoms (spheres) are colour coded: grey (silicon, Si) and green (fluorine, F).