NCERT Class XII Chapter
Atoms
Questions With Solutions
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Question : 15
Total: 18
The total energy of an electron in the first excited state of the hydrogen atom is about– 3.4 eV.
(a) What is the kinetic energy of the electron in this state?
(b) What is the potential energy of the electron in this state?
(c) Which of the answers above would change if the choice of the zero of potential energy is changed?
(a) What is the kinetic energy of the electron in this state?
(b) What is the potential energy of the electron in this state?
(c) Which of the answers above would change if the choice of the zero of potential energy is changed?
Solution:
Kinetic energy of an electron in an orbit, =
Potential energy of electron in the orbit, U = -
(
)
Total energy E = K + U = -
(
)
It is given, total energy E = (–3.4 eV)
(a) Kinetic energy of electron in this state E = – K
So, K = E = – (– 3.4 eV) = 3.4 eV
(b) Potential energy E = U/2
U = 2E = 2 (–3.4) = – 6.8 eV
(c) If the zero of the potential energy is chosen differently, the kinetic energy remain the same. Although potential energy and hence total energy changes.
Potential energy of electron in the orbit, U = -
Total energy E = K + U = -
It is given, total energy E = (–3.4 eV)
(a) Kinetic energy of electron in this state E = – K
So, K = E = – (– 3.4 eV) = 3.4 eV
(b) Potential energy E = U/2
U = 2E = 2 (–3.4) = – 6.8 eV
(c) If the zero of the potential energy is chosen differently, the kinetic energy remain the same. Although potential energy and hence total energy changes.
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