Rutherford’ s model of atom: This model explained that atom consists of nucleus which is concentrated in a very small volume. The nucleus comprises of protons and neutrons. The electrons revolve around the nucleus in fixed orbits. Electrons and nucleus are held together by electrostatic forces of attraction.
Drawbacks of Rutherford’ s model of atom:
According to Rutherford’ s model of atom, electrons which are negatively charged particles revolve around the nucleus in fixed orbits. Thus
The electrons undergo acceleration. According to electromagnetic theory of Maxwell, a charged particle undergoing acceleration should emit electromagnetic radiation. Thus, an electron in an orbit should emit radiation. Thus, the orbit should shrink. But this does not happen.
The model does not give any information about how electrons are distributed around nucleus and what are energies of these electrons
Isotopes: These are the atoms of the same element having the same atomicnumber but different mass number. e g 1H 1, 1H 2, 1H 3
Isobars: Isobars are the atoms of different elements having the same massnumber but different atomic number. e g 18Ar 40, 20Ca 40
Isoelectronic species: These are those species which have the same numberof electrons.
Electromagnetic radiations: The radiations which are associated with electrical and magnetic fields are called electromagnetic radiations. When an electrically charged particle moves under acceleration, alternating electrical and magnetic fields are produced and transmitted. These fields are transmitted in the form of waves. These waves are called electromagnetic waves or electromagnetic radiations.
Properties of electromagnetic radiations:
a. Oscillating electric and magnetic field are produced by oscillating charged particles. These fields are perpendicular to each other and both are perpendicular to the direction of propagation of the wave.