Class 12 Atoms CBSE Questions & Answers

In accordance with the Bohr’s model, find the quantum number that characterises the earth’s revolution around the sun in an orbit of radius 1.5 \( \times {\rm{ 1}}{0^{{\rm{11}}}}\) m with orbital speed 3 \( \times {\rm{ 1}}{0^{\rm{4}}}\) m/s. (Mass of earth= 6.0 \( \times {\rm{ 1}}{0^{{\rm{24}}}}\) kg.)

Average angle of deflection of \(\alpha \) -particles by a thin gold foil predicted by Thomson’s model is

Probability of backward scattering (i.e., scattering of α -particles at angles greater than \({\rm{9}}0^\circ \)) predicted by Thomson’s model is

It is found experimentally that for small thickness t, the number of α-particles scattered at moderate angles is proportional to t. What clue does this linear dependence on t provide?

In which model is it completely wrong to ignore multiple scattering for the calculation of average angle of scattering of \(\alpha \) -particles by a thin foil?

An alpha particle (charge 2e) is aimed directly at a gold nucleus (charge 79e). What minimum initial kinetic energy must the alpha particle have to approach within 5.0 * 10-14 m of the center of the gold nucleus before reversing direction? Assume that the gold nucleus, which has about 50 times the mass of an alpha particle, remains at rest.

Find the kinetic, potential, and total energies of the hydrogen atom in the first excited level, and find the wavelength of the photon emitted in a transition from that level to the ground level.

A beam of alpha particles is incident on a target of lead. A particular alpha particle comes in “head-on” to a particular lead nucleus and stops 6.5 \( \times {\rm{ 1}}{0^{ - {\rm{14}}}}\) m away from the center of the nucleus. (This point is well outside the nucleus.) Assume that the lead nucleus, which has 82 protons, remains at rest. The mass of the alpha particle is 6.64 \( \times {\rm{ 1}}{0^{ - {\rm{27}}}}\) kg . Calculate the electrostatic potential energy at the instant that the alpha particle stops. Express your result in MeV.

A beam of alpha particles is incident on a target of lead. A particular alpha particle comes in “head-on” to a particular lead nucleus and stops 6.5 \( \times {\rm{ 1}}{0^{ - {\rm{14}}}}\) m away from the center of the nucleus. (This point is well outside the nucleus.) Assume that the lead nucleus, which has 82 protons, remains at rest. The mass of the alpha particle is 6.64 \( \times {\rm{ 1}}{0^{ - {\rm{27}}}}\) kg What initial kinetic energy (in MeV) did the alpha particle have?

A beam of alpha particles is incident on a target of lead. A particular alpha particle comes in “head-on” to a particular lead nucleus and stops 6.5 \( \times {\rm{ 1}}{0^{ - {\rm{14}}}}\) m away from the center of the nucleus. (This point is well outside the nucleus.) Assume that the lead nucleus, which has 82 protons, remains at rest. The mass of the alpha particle is 6.64 \( \times {\rm{ 1}}{0^{ - {\rm{27}}}}\) kg. What was the initial speed of the alpha particle?

A hydrogen atom is in a state with energy -1.51 eV. In the Bohr model, what is the angular momentum of the electron in the atom, with respect to an axis at the nucleus?

A triply ionized beryllium ion \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\), (a beryllium atom with three electrons removed), behaves very much like a hydrogen atom except that the nuclear charge is four times as great. (a) What is the ground-level energy of \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\) ? How does this compare to the ground level energy of the hydrogen atom?

A triply ionized beryllium ion \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\), (a beryllium atom with three electrons removed), behaves very much like a hydrogen atom except that the nuclear charge is four times as great. What is the ionization energy of \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\) ? How does this compare to the ionization energy of the hydrogen atom?

A triply ionized beryllium ion \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\), (a beryllium atom with three electrons removed), behaves very much like a hydrogen atom except that the nuclear charge is four times as great. For the hydrogen atom, the wavelength of the photon emitted in the n =2 to n=1 to transition is 122 nm. What is the wavelength of the photon emitted when a \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\) ion undergoes this transition?

A triply ionized beryllium ion \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\), (a beryllium atom with three electrons removed), behaves very much like a hydrogen atom except that the nuclear charge is four times as great. For a given value of n, how does the radius of an orbit in \({\rm{B}}{{\rm{e}}^{{\rm{3}} + }}\) compare to that for hydrogen?