Question

When a hydrogen atom is raised from the ground state to an excited state.

• A. Both K.E. and P.E. increase
• B. Both K.E. and P.E. decrease
• C. The P.E. decreases and K.E. increases
• D. The P.E. increases and K.E. decreases

Answer 1

The correct option is D The P.E. increases and K.E. decreases

Potential energy of hydrogen atom is given by

$PE=\frac{-kZ{e}^2}{r}$

As atom is excited, its radius increases. But due to negative sign or reverse sign. Its actual potential energy increases.

And Kinetic energy is given by

$KE=\frac{kZ{e}^2}{2r}$

As atom is excited, its radius increases thus resulting in decrease of Kinetic energy.

Ans: The PE increases and KE decreases.