Chapter 5.2, Problem 20SSC

Interpretation Introduction

Interpretation:

The Bohr’s atomic model and the quantum mechanical model are to be compared.

Concept introduction:

The postulates of Bohr’s atomic model are written below.

• In an atom, the electron revolves around the nucleus. Electron is negatively charged and nucleus is positively charged.
• Electron revolves around the nucleus in a fixed circular path having fixed energy. These circular paths are termed as orbital shells.
The integers $\left(n=1,2,\mathrm{3....}\right)$ are termed as quantum numbers which represents the energy level. Here, $n=1$ is the lowest energy level.
• The electron moves from lower to higher energy level by gaining energy and when this electron returns to lower energy level, it releases same amount of energy in the form of electromagnetic radiation.

Answer to Problem 20SSC

Bohr’s atomic model is one dimensional model whereas quantum mechanical model is three-dimensional model. The distribution of electron in the atom is described by one quantum number in Bohr’s atomic model whereas distribution of electron in the atom is described by three quantum numbers (coordinates) in quantum model.

Explanation of Solution

The Bohr’s atomic model and the quantum mechanical model are compared as shown below.

Sr. No.	Bohr’s Atomic Model	Quantum Mechanical Model
1.	According to Bohr’s atomic model, electron revolves around the nucleus in a fixed circular path having fixed energy. These circular paths are termed as orbital shells.	According to quantum mechanical model, electron is found in 3-D space around the nucleus.
2.	In Bohr’s atomic model, electron is considered as particle.	In quantum mechanical model, electron is considered as a wave.
3.	Bohr’s atomic model is one dimensional model.	Quantum mechanical model is three-dimensional model.
4.	The distribution of electron in the atom is described by one quantum number which is principle quantum number ( n ). The principle quantum number ( n ) gives information about size of the orbit.	The distribution of electron in the atom is described by three quantum numbers (coordinates).

Conclusion

Bohr’s atomic model is one dimensional model whereas quantum mechanical model is three-dimensional model. The distribution of electron in the atom is described by one quantum number in Bohr’s atomic model whereas distribution of electron in the atom is described by three quantum numbers (coordinates) in quantum model.