# Help with a review question please Test tomorrow

Help with a review question please!!! Test tomorrow

Can you please help with this review question. My test is tomorrow and I am not sure how to do this.

Helium cation behaves like hydrogen atom. A particle with kinetic energy of 90.00 x 10^-12 erg collides with a gaseous helium cation in its ground state, quantum level n=1. After the collision, the kinetic energy of the particle is found to be 8.262 x 10^-12 erg. This event is followed by the Helium ion with the electron in quantum level n=? emitting light with a wavelength of 1214 angstroms when the electron drops to the quantum level n = 2. What is the energy of the electron in the ground electronic state, E1 of the helium atom?

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Drakkith
Staff Emeritus

Where exactly are you stuck? Please show your work you've done so far and post any applicable formulas or equations related to the problem.

Well, here is where I am.

I know that

-E(emit)=E? - E2

-E photon = hc/λ

-E2 =( -21.79 x 10 ^-12) / 4

Does this mean that E(emit) is equal to hc/λ?

If so, then hc/λ = E? - ( -21.79 x 10 ^-12) / 4

I would then take this Energy found and find what quantum level corresponds to it.

If this is correct, what do I do next? And I might be wrong somewhere