Question

Difficulty: MediumAtomic Models

According to Bohr's model of the hydrogen atom, the total energy of an electron in the first excited state (n=2n = 2) is 3.40 eV-3.40\text{ eV}. Calculate the electric potential energy of the electron in this state, in electron-volts (eV\text{eV}).

Answer: -6.8 eV

Answer

The electric potential energy of the electron in the first excited state is 6.80 eV-6.80\text{ eV}.
In Bohr's model of the hydrogen atom, an electron held in a circular orbit by electrostatic attraction has a kinetic energy K=EK = -E and an electric potential energy U=2EU = 2E. Given a total energy E=3.40 eVE = -3.40\text{ eV}, multiplying by 2 yields U=6.80 eVU = -6.80\text{ eV}.

Step-by-Step Solution

1
Identify the relationship between total energy and electric potential energy in the Bohr atomic model.
U=2EU = 2E, where UU is potential energy and EE is total energy.
For an inverse-square electrostatic force binding an electron in a circular orbit, the virial theorem dictates that kinetic energy K=EK = -E and potential energy U=2EU = 2E.
2
Substitute the given value of total energy E=3.40 eVE = -3.40\text{ eV} to solve for UU.
U=2×(3.40 eV)=6.80 eVU = 2 \times (-3.40\text{ eV}) = -6.80\text{ eV}.
Direct multiplication yields the exact electric potential energy of the bound electron.

Key Concept

Energy components (kinetic, potential, and total energy) of an electron in Bohr's atomic model
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