Question
The total energy of an electron in the ground state of a hydrogen atom is -13.6 eV. The kinetic energy of an electron in the first excited state is:
-
3.4 eV
-
6.8 eV
-
13.6 eV
-
1.7 eV
Solution
A.
3.4 eV
The total energy of an electron in the orbit is equal to negative of its kinetic energy.
The energy of hydrogen atom when the electron revolves in nth orbit is
E = -13.6/n2 eV
In the ground state: n =1
E = - -13.6/12 = -13.6 eV
For n = 2, E = -13.6/22 = -3.4 eV
so, the kinetic energy of an electron in the first excited state (i,e, for n = 2 ) is
K = - E = - (-3.4) - 3.4 eV
