Q. No.The total energy of an electron in the \(n^{th}\) stationary orbit of the hydrogen atom can be obtained by:
1. \(E_n = \frac{13.6}{n^2}~\text{eV}\)
2. \(E_n = -\frac{13.6}{n^2}~\text{eV}\)
3. \(E_n = \frac{1.36}{n^2}~\text{eV}\)
4. \(E_n = -{13.6}\times{n^2}~\text{eV}\)
1. \(E_n = \frac{13.6}{n^2}~\text{eV}\)
2. \(E_n = -\frac{13.6}{n^2}~\text{eV}\)
3. \(E_n = \frac{1.36}{n^2}~\text{eV}\)
4. \(E_n = -{13.6}\times{n^2}~\text{eV}\)
The simple Bohr model is not applicable to He4 atom because
(a) He4 is an inert gas
(b) He4 has neutrons in the nucleus
(c) He4 has one more electron
(d) electrons are not subject to central forces
1. (a, c)
2. (a, c, d)
3. (b, d)
4. (c, d)
Let be the energy of the nth level of H-atom. If all the H-atoms are in the ground state and radiation of frequency falls on it,
(a) it will not be absorbed at all
(b) some of the atoms will move to the first excited state
(c) all atoms will be excited to the n = 2 state
(d) no atoms will make a transition to the n = 3 state
1. (b, d)
2. (a, d)
3. (b, c, d)
4. (c, d)
The Balmer series for the H-atom can be observed:
| a. | if we measure the frequencies of light emitted when an excited atom falls to the ground state |
| b. | if we measure the frequencies of light emitted due to transitions between excited states and the first excited state |
| c. | in any transition in a H-atom |
| d. | as a sequence of frequencies with the higher frequencies getting closely packed |
1. (b, c)
2. (a, c)
3. (b, d)
4. (c, d)
The Bohr model for the spectra of a \(H\)-atom:
| a. | will not apply to hydrogen in the molecular form. |
| b. | will not be applicable as it is for a He-atom. |
| c. | is valid only at room temperature. |
| d. | predicts continuous as well as discrete spectral lines. |
1. (a), (b)
2. (c), (d)
3. (b), (c)
4. (a), (d)
Consider aiming a beam of free electrons towards free protons. When they scatter, an electron and a proton cannot combine to produce a H-atom,
(a) Because of energy conservation
(b) Without simultaneously releasing energy in the form of radiation
(c) Because of momentum conservation
(d) Because of angular momentum conservation
1. (b, c)
2. (a, d)
3. (a, b)
4. (c, d)
An ionised \(H\)-molecule consists of an electron and two protons. The protons are separated by a small distance of the order of angstrom. In the ground state:
| (a) | the electron would not move in circular orbits. |
| (b) | the energy would be \(2^{4}\) times that of a \(H\)-atom. |
| (c) | the electron's orbit would go around the protons. |
| (d) | the molecule will soon decay in a proton and a \(H\)-atom. |
1. (a), (b)
2. (a), (c)
3. (b), (c), (d)
4. (c), (d)
A set of atoms in an excited state decays
| 1. | in general to any of the states with lower energy |
| 2. | into a lower state only when excited by an external electric field |
| 3. | all together simultaneously into a lower state |
| 4. | to emit photons only when they collide |
Two H atoms in the ground state collide inelastically. The maximum amount by which their combined kinetic energy is reduced is:
1. 10.20 eV
2. 20.40 eV
3. 13.6 eV
4. 27.2 eV
O2 molecule consists of two oxygen atoms. In the molecule, nuclear force between the nuclei of the two atoms:
| 1. | is not important because nuclear forces are short-ranged |
| 2. | is as important as electrostatic force for binding the two atoms |
| 3. | cancels the repulsive electrostatic force between the nuclei |
| 4. | is not important because oxygen nucleus have equal number of neutrons and protons |
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