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Difference Between Work Function and the Energy Required to Remove an Electron from one Atom

Posted: Fri Oct 13, 2017 3:46 pm
by Caroline C 1G
One of the questions in the "Photoelectric Effect" post module assessment included, "How much energy is required to remove an electron from one sodium atom?" The statements before the question disclosed that the work function of sodium is 150.6 kJ/mol. I assumed that the question was simply asking for the work function, so I chose the option "1.506 x 10^5 J". However, my answer was incorrect. What is the difference between the work function of an element and the amount of energy needed to remove an electron from one atom of the element? How do you calculate this energy?

Re: Difference Between Work Function and the Energy Required to Remove an Electron from one Atom  [ENDORSED]

Posted: Fri Oct 13, 2017 5:34 pm
by Mitch Mologne 1A
The question asked for the energy for a single atom, not for a mole of sodium, while the work function was given in KJ/mol. In order to find the energy for a singular atom, divide the work function by Avogadro's number (6.022* 10^23)

Re: Difference Between Work Function and the Energy Required to Remove an Electron from one Atom

Posted: Sun Oct 15, 2017 10:26 pm
by Nora 1F
So to clarify, you are correct in thinking that the work function is equivalent to the energy needed to remove an electron from one atom of an element. This is also referred to as threshold energy. To go back to the equation, the total energy of the photon will be equal to the work function plus the kinetic energy of the electron that is removed.

E (photon) = work function + KE

Re: Difference Between Work Function and the Energy Required to Remove an Electron from one Atom

Posted: Tue Oct 17, 2017 1:28 am
by Akash_Kapoor_1L
The only thing that you forgot was the stoichiometry, you need to convert the given data from kg/mol to J/atom ... Otherwise you are correct because the Work Function is defined as the Energy Required to Remove an Electron.

Re: Difference Between Work Function and the Energy Required to Remove an Electron from one Atom

Posted: Sun Oct 22, 2017 10:09 pm
by Gobinder Pandher 3J
I agree with MitchellMologne. Although subtle, the question did ask for the energy of a single atom. A great way to tell if you need to calculate energy for a single atom is to look at the units they give for the work function. In this case it was KJ/mol. The "mol" aspect can be an indicator that you may need to calculate energy for a single atom. I hope this helps!