question_answer

 (a) State the three observations made by Rutherford on his a-particle scattering experiment. (b) Write the electronic configuration of an element whose mass number is 31 and atomic number is 15. What is its valency?  

Answer:

   (a) The three observations made by Rutherford are Most of the fast moving a ?particles passed straight through the gold foil. (ii) Some of the a-particles were deflected by the foil by small angles. (iii) Very few a-particles were completely rebounded by the gold foil.                       (b) Electronic configuration =2, 8, 5            Valency =8-5 =3