Energy needed to remove both electrons from a He atom

In summary: For removal of 2nd electron, (2) could be applied.Hence, the energy needed for removing the 2nd electron is, 27.2 * 4 eV = 108.8 eV.But, this is not given in the options.What to do now?
  • #1
Pushoam
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Homework Statement



upload_2017-12-26_18-6-27.png

Homework Equations

The Attempt at a Solution



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Both electrons are in 1s orbit.

For taking out the second electron, I will have to put slightly more energy than 24.6eV.

So, the energy required to remove both electrons should be slightly more than 49.2 eV.

So, I guess that the option should be (d)

Is this correct?
 

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  • #2
Pushoam said:
For taking out the second electron, I will have to put slightly more energy than 24.6eV.
So, the energy required to remove both electrons should be slightly more than 49.2 eV.

No. It is true that you must put more energy, but actually not so slightly. If you look at this table you can see that the second ionization energy is much higher than the first one.
TB07_002.gif

I think your problem might be that you're confusing the second ionization energy with the total energy required to take both electrons out. https://en.wikipedia.org/wiki/Ionization_energy
 

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  • #3
Dami121 said:
No. It is true that you must put more energy, but actually not so slightly. If you look at this table you can see that the second ionization energy is much higher than the first one.
View attachment 217443
I think your problem might be that you're confusing the second ionization energy with the total energy required to take both electrons out. https://en.wikipedia.org/wiki/Ionization_energy

The total energy of an electron in n th state for H- like atom is given by :

## E_n = - 13.6 eV ~\frac { Z^2}{n^2} ## ...(1)

I need to provide energy equal and opposite to the potential energy to remove an electron (taking potential energy of electron to be 0 at infinity). ## U_n = - 2 E_n = - 27.2 eV ~\frac { Z^2}{n^2} ## ...(2)

For Helium atom, for both electrons, n = 1.

Now, the ionization potential for the 1st electron could not be determined using (2) as (2) is applicable for One electron atom or ions and He – atom has 2 electrons.For removal of 2nd electron, (2) could be applied.

Hence, the energy needed for removing the 2nd electron is, 27.2 * 4 eV = 108.8 eV.So, the minimum energy required to remove both the electrons is (24.6 +108.8) eV = 133.4 eV.

But, this is not given in the options.

What to do now?
 
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  • #4
Pushoam said:
The total energy of an electron in n th state for H- like atom is given by :

## E_n = - 13.6 eV ~\frac { Z^2}{n^2} ## ...(1)

I need to provide energy equal and opposite to the potential energy to remove an electron (taking potential energy of electron to be 0 at infinity). ## U_n = - 2 E_n = - 27.2 eV ~\frac { Z^2}{n^2} ## ...(2)
This is not right. The total energy of an electron in a H- like atom is only:
## E_n = ~\frac {- 13.6 eV}{n^2} ##

Think again about what you wrote in (1) and see if you couldn't use it somehow. You're on the right track and really close to the solution.
 

What is the energy needed to remove both electrons from a He atom?

The energy needed to remove both electrons from a He atom is 54.4 electron volts (eV).

How is the energy needed to remove both electrons from a He atom calculated?

The energy needed to remove both electrons from a He atom is calculated using the equation E = (Z2 * 13.6) eV, where Z is the atomic number (2 for He).

Why is the energy needed to remove both electrons from a He atom higher than for a single electron?

The energy needed to remove both electrons from a He atom is higher because the second electron experiences a stronger nuclear attraction and is thus more difficult to remove than the first electron.

How does the energy needed to remove both electrons from a He atom compare to other elements?

The energy needed to remove both electrons from a He atom is relatively low compared to other elements, as it only has two electrons and a low atomic number. Elements with higher atomic numbers generally require more energy to remove both electrons.

How does the energy needed to remove both electrons from a He atom change in different environments?

The energy needed to remove both electrons from a He atom may change in different environments due to factors such as temperature, pressure, and the presence of other atoms or molecules. These factors can affect the stability and ionization energy of the atom, which in turn can impact the energy needed to remove both electrons.

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