# Quantum Mechanics and the Hydrogen Atom

Calculate the expectation value of the potential energy for an electron in a 1s orbital for a hydrogen atom

Ive determined the potential energy operator to be V=-e2/4∏ε0r
and a wave function of

ψ= (1/4∏)1/2

therefore i get
<V> = ∫∫∫ψ*Vψr2sin∅drd∅dphi
integrals from 0 to r, 0 to pi, 0 to 2pi

not sure where to go from here.

## The Attempt at a Solution

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Nevermind, i got it.

but if anyone is interested ill explain.

For a 1s orbital of a hydrogen the wavefunction is ψ=root(1/∏ao3 e-r/ao)

this gives
∫∫∫ψVψr2sinθdrdθd∅
integrals are zero to 2pi, zero to pi, and zero to infinity.

then factor out any terms that are not a function of r,θ, or∅.
This gives several terms outside of the integral: ∫∫∫e-2r/aorsinθdrdθd∅

then you can separate the integrals and evaluate. they were pretty easy to do.

the final answer was <v> = -e2/4∏εoao

dextercioby
Homework Helper
You can use the virial theorem. The expectation value you're looking for is then half the ground state energy.