Compare all the proposed models of an atom given in this chapter.
Answers
J.J. Thomson's model :
1)An atom is spherical in shape and comprise of positive charge with embedded negatively charged electrons .
2)The positive and the negative charges in an atom are equal and balance each other.
Rutherford's model of an atom:
1) Atom comprise positively charged, highly dense centre called the nucleus. Whole mass of an atom resides in the nucleus.
2)The electrons moves round the nucleus in circular path.
3)The size of the nucleus is very small .
Bohr's model of an atom:
1)An atom is made up of 3 particles namely ,electrons, protons and neutrons. Presence of equal number of electrons and protons, atom make the atom electrically neutral.
2) The protons and neutrons are located inside the nucleus and nucleus is positively charged.
3)The electrons revolve around the nucleus in fixed paths called orbits.
4)There is a limit to the number of electrons at each energy level can hold.
5) Each energy level has fixed amount of energy, the shell nearest to the nucleus having minimum energy and the one farthest have maximum energy.
6)There is no change in the energy of electrons as they keeping revolving in the same shell .
Explanation:
(i) An atom consists of a positively charged sphere and the electrons are embedded in it. (ii) The negative and positive charges are equal in magnitude. ... (iii) The size of the nucleus is very small as compared to the size of the atom.