Assertion (A): | Rydberg's constant does not vary with the mass number of a given element. |
Reason (R): | The reduced mass of the electron is dependent on the mass of the nucleus only. |
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): | Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate. |
Reason (R): | According to classical physics all accelerating electrons radiate. |
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): | A hydrogen atom at the ground state cannot absorb a photon of energy 10 eV. |
Reason (R): | First excitation energy of the hydrogen atom is 10.2 eV. The hydrogen atom absorbs only those photons which provide it the excitation energy. |
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): | Magnetic moment associated with an electron in hydrogen atom is quantized. |
Reason (R): | Magnetic moment associated with the electron is an integral multiple of Bohr's magneton but is independent of atomic number. |
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. |
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)
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)
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 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)
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). |