# Radial postion - momentum uncertain for 2s Hydrogen

1. Apr 8, 2013

### TheRascalKing

1. The problem statement, all variables and given/known data
I'm trying to calculate delta r * delta p for the Hydrogen atom in the 2s state

2. Relevant equations
ψ(r) = (1/ 2√π) (1 / 2a)^(3/2) (2 - (r/a)) e^(-r/2a)
where a is the bohr radius

3. The attempt at a solution
I figured out that <r> = 6a, but I'm at a loss as to how to figure out <r2> or <p>.

Using E = (-ke2 / 2a)(1/n2), and p2 = 2mE, i found <p2> = (m/2)(-ke2 / 2a), but im not 100% sure this is right

EDIT: would <p> = 0 since Hydrogen 2s is spherically symmetric?

Last edited: Apr 8, 2013
2. Apr 8, 2013

### Staff: Mentor

How did you calculate $\langle r \rangle$?

What is $k$?

No.