What is the diameter of Hydrogen?

You can look up the covalent radius of hydrogen (37 pm), and double it for the diameter. Or you can calculate the radius from Bohr's expression for the orbital radius of a hydrogen atom in the ground state: r=?2kee2mer=?2kee2me where ?=h2??=h2?, keke is the Coulomb constant, e is the charge on the electron and meme is the electron mass. This expression evaluates to 53 pm, so from this the diameter of a hydrogen atom would be 106 pm. Now, the diameter will vary somewhat based on whether the atom's in its ground state: excited states put the electron further out and are therefore larger. The covalent radius is quite a lot less than the Bohr radius because hydrogen atoms in molecules tend to be just little bumps on their neighbors. The internuclear distance for H2 is 74 pm, so you see that the covalent radius of hydrogen is 1212 of that. read less