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The potential energy of the orbital electron in the ground state of hydrogen atom is -E. What is its kinetic energy?

Asked in GUJCET 2007 · Energy levels and ionisation

• (1) 4E
• (2) 2E
• (3) E/2
• (4) E/4

Step-by-step solution

Why the other options are wrong

• (1) comes from no single slip produces 4E: in the Bohr atom the kinetic, potential and total energies are linked only by factors of 2 (K=-U/2 and total =U/2), so a factor of 4 cannot appear.
• (2) 2E turns the relation round: the size of the potential energy is twice the kinetic energy, not the other way about.
• (4) E/4 halves once too often: K is half the size of U, which is E/2, and halving again gives a value that is none of the atom's energies.

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