# Bohr model

gruba

## Homework Statement

On which orbit of hydrogen atom an electron has the speed of $734 km/s$?

## Homework Equations

Bohr's second postulate: $mvr=nh,m=9.109\cdot 10^{-31}kg,v=734 km/s,h=6.626\cdot 10^{-34} m^{2}kg/s$

## The Attempt at a Solution

By using the second Bohr's postulate, we get $$6686.006\cdot 10^{-28}r=6.626\cdot 10^{-34}n$$

Question: What is the value of radius of orbit of electron, $r$?

If we set that $r=0.0529 nm$, then we get $n=0.053$ and $n$ should be positive integer.

## Answers and Replies

Mentor
If we set that $r=0.0529 nm$
That value is for the first Bohr orbit, ##n=1##. For ##n > 1##, the radius is bigger. You need another equation relating ##r## to ##n## or ##r## to ##v##.

gruba
That value is for the first Bohr orbit, ##n=1##. For ##n > 1##, the radius is bigger. You need another equation relating ##r## to ##n## or ##r## to ##v##.

What is that equation?

Mentor
You can use the equation that balances the centripetal force and the Coulomb force. Don't you have that equation in your notes/textbook?