Q.9:- Na+ has completely filled K and L shells. Explain.   Answer:- Atomic number of sodium (Na) = 11 No. of electrons in Na = 11 No. of electrons in Na+ =…

Q.8:- Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars. Give any two uses of isotopes.   Answer:- (i) Atomic Number : The number of…

Q.7:- Define valency by taking examples of silicon and oxygen.   Answer:- The number of electrons gained, lost or shared so as to complete the octet of electrons in valence…

Q.6:- Summarize the rules for writing the distribution of electrons in various shells for the first eighteen elements.   Answer:- The distribution of elements in different orbits is governed by…

Q.5:- Compare all the proposed models of an atom given in this chapter.   Answer:- 1. J.J. Thomson’s model of atom (i)  An atom consists of a sphere of positive…

Q.4:- Describe Bohr’s model of the atom.   Answer:- The Danish physicist Neils Bohr proposed the following postulates for revising the Rutherford’s model. (a) Atom has central nucleus surrounded by…

Q.3:- What are the limitations of Rutherford’s model of the atom?   Answer:- The limitations of Rutherford’s model of the atom are following: (a) It does not explain the stability…

Q.2:- What are the limitations of J.J. Thomson’s model of the atom?   Answer:- The limitations of J.J Thomson’s model of an atom are following: (a) It could not explain…

Q.1:- Compare the properties of electrons, protons and neutrons.   Answer:- Property Electron Proton Neutron 1. Symbol  or    or     or  2. Charge  -1 unit or + 1 unit…

Q.:- Write the electronic configuration of any one pair of isotopes and isobars.   Answer:- Isotope of chloride:   Electronic configuration of each of them : 2, 8, 7 Isobars…