A particular Bohr orbit in a hydrogen atom has a total energy of - 0.28 eV. What is the kinetic energy of the electron in this orbit? What is the electric potential energy of the system?

The total energy of an electron in an orbit consists of two components

1) Potential energy which is - ve because the field is attractive

2) Kinetic energy which represents moving electron having some velocity.

Kinetic is always positive.

3) In an orbit, The magnitude of potential energy is twice that of kinetic energy. So if - 2E is the value of potential energy E wil be the value of kinetic energy.

4) Total energy will become some of potential energy and kinetic energy

-2E + E = - E

5) So total energy becomes equal to kinetic energy with only sign reversed.

In the given case total energy is - 0.28 eV. Hence kinetic energy will be + 0.28 eV.

When kinetic energy is calculated as +.28 eV, the potential energy will be

- 2 x. 28 or - 0.56 eV.