1. Which of the following is an allowed wave function for a particle in a bound state? N is a constant and α, β>0. 1) Ψ=N e-α r 2) Ψ=N(1-e-α r) 3) Ψ=Ne-α x e-β(x2+y2+z2) 4) Ψ=Non-zero constant if r<R , Ψ=0 if r>R Only one is correct. 2. What are the criteria for acceptable bound state wave functions? 3. I did assume that one of the criteria is that the wave function must go to zero at infinity. To show this, I took the limits as r goes to infinity and, for the function given in 3, as x,y,z, go to positive and negative infinty. I got that all are zero at infinity except 2. Another requirement is that the function be smooth and continuous. Since 4 has an abrupt change, i.e., its derivative is infinite at R, then it is not smooth. That leaves 1 and 3. What additional property am I forgetting?