Question

Atomic models have been improved over the years. Arrange the following atomic models in the order of their chronological order

(i) Rutherford’s atomic model

(ii) Thomson’s atomic model

(iii) Bohr’s atomic model

• A. (i), (ii) and (iii)
• B. (ii), (iii) and (i)
• C. (ii), (i) and (iii)
• D. (iii), (ii) and (i)

Answer 1

The correct option is C

(ii), (i) and (iii)

Explanation for the correct option:

Option C

William Thomson proposed the Thomson atomic model in the year$1900$.

• This theory states that an atom is made up of a positively charged sphere with embedded electrons and the atom as a whole is electrically neutral since the magnitudes of the positive and negative charges are equal.

A British scientist named Ernest Rutherford carried out an experiment, and based on the results of the experiment, he proposed the atomic structure of the elements and came up with the Rutherford Atomic Model in ($1911$).

• Most of the space in an atom is unoccupied because a significant portion of the -particles bombarded towards the gold sheet went through the sheet without any deflection.
• The positive charge in an atom is not uniformly distributed or is concentrated in a very tiny volume as a result of some of the -particles being deflected by the gold sheet at very small angles.

Neil Bohr proposed the Bohr model of the atom in$1915$.

• According to this model in an atom, negatively charged electrons travel in fixed circular paths around the positively charged nucleus that is referred to as orbits or shells.
• Each orbit or shell has defined energy.
• The quantum number ($\mathrm{n}=1,2,3,$ etc.), which is an integer, is used to indicate the energy levels. This quantum number range begins on the nucleus side, which has the lowest energy level.
• A lower energy level to a higher energy level is reached by an atom's electrons by gaining the necessary energy, and a higher energy level to a lower energy level by losing energy.

Explanation for the incorrect options:

Option (A): (i), (ii) and (iii)

1. The Rutherford atomic model was proposed in $1911$ whereas the Thomson atomic model was proposed in the year$1900$
2. Hence, it is an incorrect option.

Option (B): (ii), (iii) and (i)

1. The Rutherford atomic model was proposed in $1911$whereas the Bohr model of the atom was proposed in$1915$.
2. Hence, it is an incorrect option

Option (D): (iii), (ii) and (i)

1. The Bohr model of the atom was proposed in$1915$ whereas the Thomson atomic model was proposed in the year $1900$
2. Hence, it is an incorrect option

Final answer: The correct chronological order for the atomic models is (ii), (i), and (iii)