Q. No.Atomic number of H-like atom with ionization potential \(122.4~\text{V}\) for \(n=1\) is:
1. \(1\)
2. \(2\)
3. \(3\)
4. \(4\)
1. \(1\)
2. \(2\)
3. \(3\)
4. \(4\)
What is the shortest wavelength present in the Paschen series of spectral lines?
1. \(818.9~\text{nm}\)
2. \(779~\text{nm}\)
3. \(500~\text{nm}\)
4. \(1024~\text{nm}\)
(\(m_e\) represents mass of electron)
| 1. | \(0.53 \times 10^{-13} ~\text{m},-3.6 ~\text{eV}\) |
| 2. | \(25.6 \times 10^{-13} ~\text{m},-2.8 ~\text{eV}\) |
| 3. | \(2.56 \times 10^{-13} ~\text{m},-2.8 ~\text{keV}\) |
| 4. | \(2.56 \times 10^{-13} ~\text{m},-13.6 ~\text{eV}\) |
For which one of the following Bohr models is not valid?
| 1. | Singly ionised helium atom \(\big(\mathrm{He}^{+}\big).\) |
| 2. | Deuteron atom. |
| 3. | Singly ionised neon atom \(\big(\mathrm{Ne}^{+}\big).\) |
| 4. | Hydrogen atom. |
The ionisation potential of the hydrogen atom is \(13.6~\text{eV}.\) The hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy of \(12.1~\text{eV}.\) According to Bohr’s theory, the spectral lines emitted by hydrogen atoms will be:
1. two
2. three
3. four
4. one
The wavelength of the first line of the Lyman series for a hydrogen atom is equal to that of the second line of the Balmer series for a hydrogen-like ion. What is the atomic number \(Z\) of hydrogen-like ions?
1. \(4\)
2. \(1\)
3. \(2\)
4. \(3\)
What happens when an electron makes a transition from an excited state to the ground state of a hydrogen-like atom or ion?
| 1. | Its kinetic energy increases but potential energy and total energy decrease. |
| 2. | Kinetic energy, potential energy and total energy decrease. |
| 3. | Kinetic energy decreases, potential energy increases but the total energy remains the same. |
| 4. | Kinetic energy and total energy decrease but potential energy increases. |
An ionised \(\text H\)-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 \(\text H\)-atom. |
| (c) | the electron's orbit would go around the protons. |
| (d) | the molecule will soon decay in a proton and a \(\text H\)-atom. |
Choose the correct option:
| 1. | (a), (b) | 2. | (a), (c) |
| 3. | (b), (c), (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. |
Choose the correct option:
| 1. | (a), (b) | 2. | (c), (d) |
| 3. | (b), (c) | 4. | (a), (d) |
The de-Broglie wavelength of an electron in the second orbit of a hydrogen atom is equal to:
| 1. | The perimeter of the orbit. |
| 2. | The half of the perimeter of the orbit. |
| 3. | The half of the diameter of the orbit. |
| 4. | The diameter of the orbit. |
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