Q71. Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

 

Q72. Match the names of the Scientists given in column A with their contributions towards the understanding of the atomic structure as given in column B.

Column (A)

Column (B)

(a) Ernest Rutherford

(i) Indivisibility of atoms

(b) JJ.Thomson

(ii) Stationary orbits

(c) Dalton

(iii) Concept of nucleus

(d) Neils Bohr

(iv) Discovery of electrons

(e) James Chadwick

(v) Atomic number

(f) E. Goldstein

(vi) Neutron

(g) Mosley

(vii) Canal rays

 

Q73. How will you find the valency of chlorine, sulphur and magnesium?

 

Q74. Compare all the proposed models of an atom given in this chapter. 

 

Q75. Explain with examples (i) Atomic number, (ii) Mass number,

(iii) Isotopes and iv) Isobars. Give any two uses of isotopes.

 

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