Question 1

According to Thomson's atomic model, what is the distribution of positive charge and electrons in an atom?

Accepted Answer

According to Thomson's atomic model (plum pudding model), the positive charge is uniformly distributed throughout the spherical volume of the atom, and the electrons are embedded inside it like plums in a pudding to maintain electrical neutrality.

Question 2

In Geiger-Marsden scattering experiment (alpha-particle scattering), most of the alpha particles:

Accepted Answer

In the alpha-particle scattering experiment, most of the alpha particles passed straight through the gold foil with little or no deflection, which proved that the atom is mostly empty space.

Question 3

The distance of closest approach of an alpha particle to the nucleus of atomic number Z is given by which proportional relationship?

Accepted Answer

The distance of closest approach (r0) is obtained by equating the kinetic energy of the alpha particle to the electrostatic potential energy at that distance, which gives r0 proportional to 1/E (where E is kinetic energy) and directly proportional to Z.

Question 4

According to Rutherford's atomic model, the electrons in an atom are:

Accepted Answer

Rutherford proposed that electrons revolve around the dense, positively charged nucleus in circular orbits, just like planets revolve around the sun, with electrostatic force providing the necessary centripetal force.

Question 5

What is the primary failure of Rutherford's nuclear model of the atom?

Accepted Answer

According to classical electromagnetic theory, an accelerated charged electron should continuously radiate energy and spiral into the nucleus, making the atom unstable. However, atoms are stable.

Atoms — MP Board Class 12 Physics Important Questions & Revision Notes