Deriving the electron speed from a specified orbital

[jason0294]

[Mentor's note: this thread was moved from a non-homework forum, therefore it does not use the normal template for homework questions]

What is the speed of the electron in terms of the speed of the light when it is in the n = 3 state in the Hydrogen atom?

I started with this equation to find the energy En=-E0(z^2/n^2)
From that i used the momentum=E/c and found momentum then derived v from p=mv
The system keeps saying I am wrong, is there anything specific I am missing or maybe an equation i should be using instead?

 

[ehild]

What is the speed of the electron in terms of the speed of the light when it is in the n = 3 state in the Hydrogen atom?

I started with this equation to find the energy En=-E0(z^2/n^2)
From that i used the momentum=E/c and found momentum then derived v from p=mv

Read http://en.wikipedia.org/wiki/Energy–momentum_relation

Is E=pc true for an electron?

The total energy of the electron in the Hydogen atom is negative. What do you think, why?

ehild