Choose the correct alternative from the clues given at the end of the each statement:
(c) A classical atom based on .......... is doomed to collapse.

(a) Using the Bohr’s model calculate the speed of the electron in a hydrogen atom in the $n = 1, 2$, and $3$ levels.

Choose the correct alternative from the clues given at the end of the each statement:
(d) An atom has a nearly continuous mass distribution in a .......... but has a highly non-uniform mass distribution in ..........

Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K.) What results do you expect?

Choose the correct alternative from the clues given at the end of the each statement:
(e) The positively charged part of the atom possesses most of the mass in ..........

(b) Calculate the orbital period in each of these levels.

The radius of the innermost electron orbit of a hydrogen atom is $5.3 \times 10^{-11}$ m. What are the radii of the $n = 2$ and $n = 3$ orbits?

Choose the correct alternative from the clues given at the end of the each statement:
(a) The size of the atom in Thomson’s model is .......... the atomic size in Rutherford’s model.

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 $1.5 \times 10^{11}$ m with orbital speed $3 \times 10^{4}$ m/s. (Mass of earth = $6.0 \times 10^{24}$ kg.)

A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. What series of wavelengths will be emitted?

Choose the correct alternative from the clues given at the end of the each statement:
(b) In the ground state of .......... electrons are in stable equilibrium, while in .......... electrons always experience a net force.

The ground state energy of hydrogen atom is –13.6 eV. What are the kinetic and potential energies of the electron in this state?

A difference of 2.3 eV separates two energy levels in an atom. What is the frequency of radiation emitted when the atom make a transition from the upper level to the lower level?

A hydrogen atom initially in the ground level absorbs a photon, which excites it to the $n = 4$ level. Determine the wavelength and frequency of photon.