What were the drawbacks of Rutherford’s atomic model?
Rutherford’s atomic model explained the structure of atoms. However, it was not theoretically
appropriate.
We know that a body in circular motion undergoes acceleration and liberates energy. This means that electrons revolving around a nucleus are accelerating and giving out energy as well. This should reduce the energy of electrons and they will start descending into orbits of lower energy, ultimately leading to a collapse of electrons into the nucleus. However, it is observed that all atoms are stable, and no such collapse takes place.
This meant that the hypothesis put forth by Rutherford was not entirely correct and it led Neils Bohr to bring in new modifications to the atomic model.
What is Bohr’s Model?
The postulates put forward by Niels Bohr were:
- Only certain special orbits called discrete orbits of electrons are allowed inside the
- While revolving in these discrete orbits, the electrons do not radiate
This explains the stability of an atom. But the atomic model was yet not complete.
Niels Bohr
Discovery of neutrons
Combining the postulates of Rutherford and Bohr, people came up with an atomic structure. But this structure was not completely right until 1932 when a famous English physicist Sir James Chadwick discovered the third subatomic particle.
This particle was electrically neutral and had a mass, almost equal to the mass of a proton. The
particle was named as Neutron, denoted by the letter ‘n’.
Sir James Chadwick
What is the modern-day Atomic structure?
The atomic structure is like our solar system with the nucleus at the centre like the Sun and the electrons revolving around it in fixed orbitals, just like planets.
Atomic structure
These electron orbitals are known as Shells or Energy levels. The electrons do not radiate energy, and each shell has got a defined energy level.
We name these shells as K shell, L shell, M shell, N shell, etc.
To number them, we use the letter ‘n’ in lowercase and write them as n=1, n=2, n=3, and so on.
Shell naming
The nucleus is at the centre containing positively charged protons and neutral neutrons. Negatively charged electrons revolve around the nucleus. This is the general structure of an atom.
