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 .