Why Does Diatomic Hydrogen Form Despite Zero Net Electric Field?

[Tom MS]

Say you had two isolated hydrogen atoms. Because of the spherical distribution of electronic charge on each hydrogen and the net charge of 0 outside each atom, wouldn't Gauss's law dictate a 0 net electric field outside each atom? If this is the case, why does diatomic hydrogen so readily form?
I know that in extremely low pressure, low temperature situations in space, there are large clouds of atomic hydrogen, so do random thermal collisions bring hydrogen into its diatomic state?

 

[DrClaude]

Say you had two isolated hydrogen atoms. Because of the spherical distribution of electronic charge on each hydrogen and the net charge of 0 outside each atom, wouldn't Gauss's law dictate a 0 net electric field outside each atom? If this is the case, why does diatomic hydrogen so readily form?

While an isolated atom in its ground state has no dipole moment, two atoms will induce dipoles in each other. This is known as the van der Waals interaction. (Classically, you can see it as the charge distribution of the electron as being isotropic on average, but not at any given instant.)

I know that in extremely low pressure, low temperature situations in space, there are large clouds of atomic hydrogen, so do random thermal collisions bring hydrogen into its diatomic state?

Two colliding hydrogen atoms will not form a molecule, as there is no fast decay channel through emission of a photon. You need three-body collisions, or interaction via a surface, to be able to take the bonding energy away and be left with a stable molecule.