# Ionization energy

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1. Jun 17, 2016

### physicsmaths1613

1. The problem statement, all variables and given/known data
The energy required to ionize a helium atom is 24.6 eV. The energy required to remove both the electrons from He atom would be?

3. The attempt at a solution
My textbook says-
IP1= 24.6 eV
IP 2= IP1*Z2
How can they relate the first ionization energy to the second one? The Bohr's atom can be used only for Hydrogen like species and He atom is not Hydrogen like, only it's ion is. How did they relate it?

2. Jun 17, 2016

### harsh_sinha

He+ is a hydrogen like species as it has one electron.So Bohr's model is applicable on it.

3. Jun 17, 2016

### physicsmaths1613

But what about intial He atom with 2 electrons?

4. Jun 17, 2016

### harsh_sinha

Bohr's model is not applicable for He atom.Besides if we use this equation to calculate IP2 then the result would be twice of the actual value.
It would be great if you share the source of this equation.

5. Jun 17, 2016

### haruspex

I can only get the right answer from that by interpreting the IP2 as the energy to remove the second electron from He+, and the IP1 as the energy required to ionise H (which makes sense).