(Note: All previous parts in the Complexity Explained series by Dr. Vinod Wadhawan can be accessed through the ‘Related Posts’ listed below the article.)
How did life originate on Earth? Chemical or molecular evolution preceded the emergence of life. Under the influx of low-entropy energy from the 
Sun, and aided by the presence of certain rocks, atoms and molecules underwent chemical reactions resulting in the emergence of molecules of higher and higher information content or complexity. This article explains how this occurred.
8.1 From Atoms to Molecules
The chemical symbol H is used for an atom of hydrogen, which is the first element in the periodic table of elements. It has a nucleus, which is just a proton in this case, and there is an electron orbiting around the nucleus. The electron has a negative charge, exactly equal in magnitude to the positive charge of the proton. Taking this quantity as the unit of charge, we say that an H atom has a charge number 1 (Z = 1). Taking the mass of the proton as the unit mass, we say that H has a mass number 1 (A = 1). The electron is ~2000 times lighter than the proton. Read the full story
