Selina Concise Physics Class 10 ICSE Solutions Radioactivity Selina ICSE Solutions for Class 10 Physics Chapter 12 Radioactivity Exercise 12(A) 1.Name the three constituent of an atom and state their mass and charge of each. How are they distributed in an atom? Solution 1. Three constituent of an atom are: Electrons: mass is 9.1 x 10-31 kg, charge is -1.6 x 10-19C Neutron: mass is 1.6749 x 10-27 kg, charge is zero. Protons: mass is 1.6726 x 10-27 kg, charge is +1.6 x 10-19 C 2.Define the terms: (a)Atomic number and(b) mass number. Solution 2 . Atomic number – the number of protons in the nucleus is called atomic number. Mass number – the total number of nucleons in the nucleus is called mass number. 3.What is nucleus of an atom? Compare its size with that of the atom. Name its constitutents. How is the number of these constituents determined by the atomic number its atomic model. Solution 3. The nucleus at the centre of atom, whose...
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