The simple Bohr model is not applicable to \(\text{He}^4\) atom because:
(a) | \(\text{He}^4\) is an inert gas. |
(b) | \(\text{He}^4\) has neutrons in the nucleus. |
(c) | \(\text{He}^4\) has one more electron. |
(d) | electrons are not subject to central forces. |
Choose the correct option:
Let \(E_{n} = \dfrac{- 1}{8 \varepsilon_{0}^{2}} \dfrac{m e^{4}}{n^{2} h^{2}}\) be the energy of the \(n^\text{th}\) level of H-atom. If all the H-atoms are in the ground state and radiation of frequency \(\dfrac{\left(\right. E_{2} - E_{1} \left.\right)}{h}\) falls on it, then:
(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. |
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) |
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. |
Assertion (A): | When light consisting of wavelengths corresponding to the Balmer series is incident on a gas containing \(\mathrm{He}^{+}\) ions in the first three excited states - it can be absorbed by the \(\mathrm{He}^{+}\) ions. |
Reason (R): | All the energy levels of the \(\mathrm{He}^{+}\) ions are the same as those of the \(\mathrm{H}\) atoms. |
1. | (A) is True but (R) is False. |
2. | (A) is False but (R) is True. |
3. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
4. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
Assertion (A): | \(n.\) | The magnetic moment of a hydrogen-like atom is higher when it is in a state of higher quantum number
Reason (R): | \(n.\) | The magnetic moment of hydrogen-like atom, as calculated from Bohr's theory, is directly proportional to the principal quantum number
1. | (A) is True but (R) is False. |
2. | (A) is False but (R) is True. |
3. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
4. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
Assertion (A): | The positively charged nucleus of an atom has a radius of almost \(10^{-15}~\text{m}\). |
Reason (R): | I\(\alpha\)-particle scattering experiment, the distance of the closest approach for \(\alpha\)-particle is \(\approx 10^{-15}~\text m\). | n
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |
Assertion (A): | The hydrogen atom consists of only one electron but its emission spectrum has many lines. |
Reason (R): | Only Lyman series is found in the absorption spectrum of hydrogen atoms whereas in the emission spectrum, all the series are found. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |