The formula for hydrogen sulfide is H2S. This molecule consists of two atoms of hydrogen bonded to one atom of sulfur. Hydrogen sulfide exists as a naturally occurring gas.
Hydrogen sulfide is colorless but possesses a characteristic odor reminiscent of rotten eggs. The bonds between the hydrogen and sulfur atoms in hydrogen sulfide are similar to the bonds between hydrogen and oxygen atoms in water, but because oxygen is a more electronegative atom than sulfur, water is more polar than hydrogen sulfide. This means that the bonds holding water molecules together are stronger than the bonds holding hydrogen sulfide molecules together. Having fewer polar bonds than water, hydrogen sulfide has lower melting and boiling points.