Compare all the proposed models of an atom given in this chapter.

Explanation

In this chapter, four atomic models were discussed. The main postulates of those models are
1. Dalton's proposal :
a) Atomic are indivisible.
b) Atoms of an element are all identical to each other and different from the atoms of other elements.
2. Thomson's proposal :
a) An atom is considered to be a sphere of uniform positive charge and electrons are embedded into it.
b) The total mass of the atom is considered to be uniformly distributed throughout the atom.
3. Rutherford's proposal :
a) All the positively charged material in an atom formed a small dense centre, called the nucleus of the atom.
b) Negatively charged electrons revolve around the nucleus in well defined orbits.
c) Size of the nucleus is very small as compared to the size of the atom.
4. Neils Bohr's proposal :
a) Electrons are revolving around the nucleus in special, discrete orbits called energy levels or shells.
b) While revolving in these discrete orbits the electron do not radiate energy and this helps that the electrons do not crash into the nucleus.
c) These orbits or shells are represented by the letters K, L, M, N, .............. or the numbers n = 1, 2, 3, .................