# How is hydrogen more stable in diatomic form?

## Main Question or Discussion Point

Hello Physicsforums,

I'm curious to know what stability hydrogen receives through adding one more electron to its 1s sublevel level. The whole sublevel is at the same energy state, so why must it fill that one more space to attain stability? What does a full 1s orbital do to make it stable? I can see why it's inert, but we stay it's more stable.

Thanks,

Vanmaiden

## Answers and Replies

Simon Bridge
Homework Helper
Is molecular hydrogen said to be more stable than atomic hydrogen? Who by? And in what context?

You need 13.6eV to break apart a H atom, but only 4.6eV to break apart an H2 molecule.

The stability of a covalent bond is a QM effect from symmetry.
Paired electrons in sub-shells sort-of "balance out the load" on an atom.
But you should be aware that molecular energy levels are not the same as the atomic ones.

http://www.eng.fsu.edu/~dommelen/quantum/style_a/hmol.html
http://hyperphysics.phy-astr.gsu.edu/hbase/molecule/hmol.html

The reasoning here is the same as for all elements: the octet rule.
The only difference is that hydrogen and helium are so simple that their "octet" is only two atoms.

This stuff is really all about geometry. Everything in the universe is in a 3d matrix (well, 4d really, but we're being simplistic here). If there are electrons on opposite sides of a proton then everything is much more stable. Imagine... imagine a tight rope walker. When he's walking along the rope holding nothing, he's able to balance and move forward slowly. Give him a pole and he has some weight balancing him out horizontally, and he can move along a bit more steadily. Make him carry a weight in one hand though, and
he's less stable.
(Keep in mind that this is a completely different set of rules [kinetics], but I hope that it helps to illustrate the point a little.)

Simon Bridge
Homework Helper
Though electrons in the ground state of hydrogen are symmetrically distributed ... but it's balanced here to pair spin-up and spin-down.

DrDu