# Why is the ionization energy for Hydrogen non-zero?

There are no other electrons to collide, repel and kick Hydrogen's single electron to a distant nucleus. And that a single electron is tightly attracted to the nucleus by the electrostatic energy between them. So it seems to me, that Hydrogen does not require ionization energy at all.

But when I checked on the sources - the Hydrogen's ionization energy is relatively high.

Even Hydrogen makes $NaH$, which just doesn't stay for long and has extreme need for becoming $Na$ metal and Hydrogen gas.

So in this case why can't we say that Hydrogen does not require ionization energy?

• I'm unfamiliar with the term ionic energy. By ionic energy, do you mean ionization energy? – John Snow Sep 11 '14 at 22:37
• I think that ionization-energy is a borderline case when it comes to tags, electrostatic-energy on the other hand is completely superfluous. – Martin - マーチン Sep 12 '14 at 16:57
• @Martin I have no intention of earning 2reps on tag wiki. I just created them, because the context of my question refers to those. – bonCodigo Sep 12 '14 at 17:04
• That's alright, we'll see how they play out... – Martin - マーチン Sep 12 '14 at 17:09

The ionization energy (IE) of an atom or molecule describes the minimum amount of energy required to remove an electron (to infinity) from the atom or molecule in the gaseous state.

With ionization energy, an electron is not "kicked out" by other electrons, but rather it is "the energy required for the electron to 'climb out' and leave the atom."

Since the electron "is drawn inwards by positive electrostatic potential," it would make sense to infer that the more "tightly drawn" the electron is to the nucleus, the more energy it would require to "climb out."

• @bonCodigo It's a bit related. I'd generally revert to electronegativity arguments when discussing whether there are ionic or covalent bonds. The electronegativity of H is almost the same as C, so it does tend to form covalent bonds. NaH and LiH (any hydride) involves $H^-$. In this case, the extra electron in hydride anion is NOT tight or close, making it extra reactive. – Geoff Hutchison Sep 12 '14 at 17:49