Normalizing the wave function of the electron in hydrogen

10 replies · 6K views · last reply
Cocoleia
Messages
293
Reaction score
4

Homework Statement


Printed textbook problem: the normalized ground-state hydrogen wavefunction psi(r, theta, phi) = (1/sqrt(pi)) (1/a0)^(3/2) e^(-r/a0), with parts (a) to (e) listed below it.

I am having trouble with part d, where they ask me to prove that the wave function is already normalized

The Attempt at a Solution


Handwritten derivation of the normalization integral for a hydrogen ground-state wavefunction in spherical coordinates, reducing to 8π a0^3 − 4π e^(−r/a0)(2a0^2 + 2a0 r + r^2) over π a0^3.

But that clearly doesn't give me 1. I tried to use spherical coordinates since it is in 3D? Not really sure how to proceed.
EDIT: I realize that I didn't square the wave function, so
Integral from 0 to r of (e^(-r/a))^2 r^2 dr equals (1/4) a (a^2 - e^(-2r/a) (a^2 + 2ar + 2r^2)), written as typeset mathematics.

Which still doesn't give me 1
 
blue_leaf77 said:
The integration limit should be from ##0## to ##\infty##.
Ok. I was thinking 0 to r since the most it could go was to the radius. I guess the logic is wrong
Integral from 0 to infinity of (e^(-r/a))^2 r^2 dr equals a^3/4 for Re(1/a) > 0.

multiplied by 4pi, so the 4's will cancel out, leaving me with (a_0^3)(pi)
Which still doesn't = 1. What am I missing
 
It pays to be methodical
##\psi(r,\theta,\phi) =\frac{1}{\sqrt{\pi}} \left( \frac{1}{a_0} \right )^{3/2} e^{-r/a_0}##
##\psi^*(r,\theta,\phi) \psi(r,\theta,\phi) =\frac{1}{{\pi}} \left( \frac{1}{a_0} \right )^{3} e^{-2r/a_0}##
Now do the integrals.
 
kuruman said:
It pays to be methodical
##\psi(r,\theta,\phi) =\frac{1}{\sqrt{\pi}} \left( \frac{1}{a_0} \right )^{3/2} e^{-r/a_0}##
##\psi^*(r,\theta,\phi) \psi(r,\theta,\phi) =\frac{1}{{\pi}} \left( \frac{1}{a_0} \right )^{3} e^{-2r/a_0}##
Now do the integrals.
If I use the spherical coordinates I still get (a^3)π. I say that 0<Θ<π and 0<Φ<2π
 
Cocoleia said:
If I use the spherical coordinates I still get (a^3)π. I say that 0<Θ<π and 0<Φ<2π
Can you show the expression that you integrated to get this result?
 
kuruman said:
Can you show the expression that you integrated to get this result?
Handwritten integral: (1/π)(1/a0)^3 times the integral from 0 to infinity of e^(-2r/a0) r^2 dr, times the integral from 0 to π of sinθ dθ, times the integral from 0 to 2π dφ.

I took out the constant and then used spherical coordinates
 
Cocoleia said:
View attachment 117362
I took out the constant and then used spherical coordinates
Oh wait. I think I figured it out. I lost my constant along the way.
When I integrate to find the probability of finding the electron in a certain place will I use spherical coordinates again ?
 
Is it true that the probability of finding electron betwee r1= ao/2 and r2= 3a0/2 is 49,65%? For this problem
 
rb120134 said:
Is it true that the probability of finding electron betwee r1= ao/2 and r2= 3a0/2 is 49,65%? For this problem
Yes.
 
  • Like
Likes   Reactions: PeroK