# Force between nucleus and electron [duplicate]

Let's say we have a hydrogen atom in electric field. If the field is strong enough, electron will be separated from nucleus. How to determine the value of $$E$$ at which it happens?

To my understanding, field pulls electron with force $$eE$$ in one direction and proton with the same force to another. But how to determine the force holding them together?

EDIT: I am asking specifically how to calculate the value $$E$$ of external electric field which is "just enough" to ionize the atom.

## marked as duplicate by StephenG, ZeroTheHero, Sebastian Riese, user191954, John Rennie homework-and-exercises StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Sep 25 '18 at 7:21

• See these duplicate answers: physics.stackexchange.com/q/384241 and this physics.stackexchange.com/q/44007 – Paul Sep 24 '18 at 18:06
• Possible duplicate of Can electromagnetic fields be used to deconstruct and reconstruct atoms? – Paul Sep 24 '18 at 20:50
• @Paul, I do not think any of the links you provided actually answers this question with all the math involved. All the answers are qualitative, not quantitative. See the EDIT. There is one answer by Emilio Pisanty which is good for Fermi estimation. Better than nothing, but still, I do not agree that this question is duplicate. – FiatLux Sep 24 '18 at 21:06
• @FlatLux The answers in the links posted explain some possible different mechanisms and give estimates in at least one case in terms of the magnitude of an electric field. The point here is that there is more than one way to achieve what you've asked and the links indicate what you should look at next. Perhaps you could choose one of the mechanisms, try a calculation, and then post to receive further help if needed? – Paul Sep 26 '18 at 21:34