Is H2S Polar or Nonpolar?

Answer: H2S is a polar molecule due to the presence of lone pair electrons at the top of the molecule causing a region of partial negative charge due to electron-electron repulsion. 

H2S has a very similar structure as H2O (see the lewis dot structure for H2O and the polar/nonpolar explanation at the linked addresses). However, due to the larger size of the sulfur atom compared to oxygen, the bond angle (i.e. the smaller angle between the two hydrogen atoms) is only 92˚ compared to 107.5˚ for H2O. Sulfur contains many more electrons which ultimately due to electron-electron repulsion require a lot more space. Nevertheless the decreased electronegativity of sulfur when compared to hydrogen (2.58 vs. 2.20, respectively) means that the molecule is much less polar overall when compared to H2O. This means that it has a much lower melting and boiling point at -82˚C and -60˚C, respectively. Like SO2 the presence of sulfur means that this molecule has a pungent odor in gaseous form although it is colorless. 

H2S Ball and Stick Diagram
H2S Ball and Stick Diagram. Created with MolView.

How is H2S utilized in the real world?

Hydrogen sulfide appears in many different ways within the natural world. For starters it is an important constituent of the sulfur cycle. Bacteria oftentimes convert the sulfur from organic elements to inorganic molecules such as H2S. The main use of hydrogen sulfide is as a storage compound which can be converted to pure sulfur during reactions to form all kinds of sulfur-containing compounds. Hydrogen sulfide may have also caused a mass extinction due to its buildup within the atmosphere. Based on this fact it is not difficult to imagine the toxicity of hydrogen sulfide towards life forms such as human beings. It negatively impacts proper nervous system functioning primarily although it will affect other body systems as well. Nevertheless there are certain organisms adapted to live in high-H2S conditions due to those environments existing in deep underwater volcanic sea vents.  

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