Atoms

The total energy of an electron in the first excited state of

Physics Part-II

Class 12

NCERT

Chapter 1: Ray Optics and Optical Instruments

41 questions

Chapter 2: Wave Optics

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Chapter 3: Dual Nature of Radiation and Matter

44 questions

Chapter 4: Atoms

23 questions

12.14.

Classically, an electron can be in any orbit around the nucleus of an atom. Then what deteres the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? The question had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as follows with the basic constants of nature and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom

(1 0^{- 10} m)

(a) Construct a quantity with the dimensions of length from the fundamental constants

e, m_{e}, an d c

. Detere its numerical value.

The total energy of an electron in the first excited state of the hydrogen atom is about

- 3.4 e V

(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?

If Bohrs quantisation postulate (angular momentum =

nh / 2 π

) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why then do we never speak of quantisation of orbits of planets around the sun?

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Chapter 5: Nuclei

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Solving time: 5 mins

The total energy of an electron in the first excited state of the hydrogen atom is about $- 3.4 e V$ .
$(a)$ 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?

Name: Video answer for The total energy of an electron in the first excited state of the hydrogen atom is about −3.4eV.(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? - Physics Part-II
Uploaded: 2022-12-06T02:19:17.000Z
Duration: 7 min
Description: [Solved] The total energy of an electron in the first excited state of the hydrogen atom is about −3.4eV.(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? - Physics Part-II

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Updated on: Dec 6, 2022

Book:

Physics Part-II (NCERT)

Text solutionVerified

In Bohrs model, mvr = nh and

\frac{m v ^{2}}{r} = \frac{Z e ^{2}}{4 π ε _{0} r ^{2}}

, which give,

T = \frac{1}{2} m v^{2} = \frac{Z e ^{2}}{8 π ε _{0} r}; r = \frac{4 π ε _{0} h ^{2}}{Z e ^{2} m} n^{2}

These relations have nothing to do with the choice of the zero of potential energy. Now, choosing the zero of potential energy at infinity, we have

V = - (Z e^{2} /4 π ε_{0} r)

, which gives

V = - 2 T

and

E = T + v = - T

(a) The quoted value of E = 3.4 eV is based on the customary choice of zero of potential energy at infinity. Using E = T, the kinetic energy of the electron in this state is + 3.4 eV.

(b) Using V = 2T, potential energy of the electron is = 6.8 eV.

(c) If the zero of potential energy is chosen differently, kinetic energy does not change. Its value is + 3.4 eV independent of the choice of the zero of potential energy. The potential energy, and the total energy of the state, however, would alter if a different zero of the potential energy is chosen.

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The total energy of an electron in the first excited state of the hydrogen atom is about

- 3.4 e V

(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?

6 mins ago

Discuss this question LIVE

6 mins ago

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Practice more questions from Physics Part-II (NCERT)

12.14.

(1 0^{- 10} m)

(a) Construct a quantity with the dimensions of length from the fundamental constants

e, m_{e}, an d c

. Detere its numerical value.

The total energy of an electron in the first excited state of the hydrogen atom is about

- 3.4 e V

(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?

If Bohrs quantisation postulate (angular momentum =

nh / 2 π

) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why then do we never speak of quantisation of orbits of planets around the sun?

View all

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Question Text	The total energy of an electron in the first excited state of the hydrogen atom is about $- 3.4 e V$ . $(a)$ 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?
Updated On	Dec 6, 2022
Topic	Atoms
Subject	Physics
Class	Class 12
Answer Type	Text solution:1 Video solution: 1
Upvotes	137
Avg. Video Duration	7 min

Text solutionVerified

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