# How much energy is required to make an ion?

So say that I have a normal hydrogen atom (not an isotope, just regular normal hydrogen atom) and I want to make it into an ion $\text{H}^+$. Since to make an ion of that formula I need to take away an electron, it is just the same as giving the electron energy for it to transition from quantum energy level 1 to level $\infty$, so I use the energy level formula for the hydrogen atom $E_n = -\frac{1312}{n^2}$ and substitute $n$ for $1$ and $\infty$ to get $-1312 \text{ kJ/mol}$ and $0\text{ kJ/mol}$ respectively. So if I add 1312 $\text{kJ/mol}$ of energy to the electron it should leave the atom, right? But my textbook says it is wrong.

• What value does your textbook give? – Todd Minehardt Jul 28 '15 at 1:17
• This was actually a multiple choice question that gives a bunch of choices and asks which of these choices are correct. However, when I got to this choice and solved it out, I got the answer like above and the choice to me was correct. The textbook however, said a different choice was the correct choice. – phi2k Jul 28 '15 at 1:18
• Might be a sign error - meaning, you have to put in 1312 kJ/mol, so it would be a positive and not negative number. Was that a choice? – Todd Minehardt Jul 28 '15 at 1:20
• No, I got the answer that the choice gave, and it was positive. – phi2k Jul 28 '15 at 1:21
• Is the problem that you need the energy for a single ion rather than a mole? – Nicolau Saker Neto Jul 28 '15 at 1:32