Bihar BoardEnglish MediumSTD 12 SciencePhysicsNUCLEI3 Marks
Question
Define the different terms used for the composition of a nucleus.
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Answer
• The Composition of nucleus : (i) Atomic number $( Z )$ : →The number of electrons in the neutral atom is called the atomic number. OR →The number of protons in the neutral atom is called the atomic number. (ii) Mass number (A) : →The sum of the number of protons and neutrons in the nucleus of the atom is called the atomic mass number A . →Both protons and neutrons are present in the nucleus hence it is known by the common name of nucleon. →The total number of nucleons in the nucleus of an atom is called atomic mass number A . $\therefore A = Z + N$ (iii) Neutron number ( N $)$ : →The number of neutrons present in the nucleus of an atom is called the neutron number N . (iv) Nuclide : →The type of nucleus is called nuclide and is represented by symbol ${ }_Z X^A$. →Where X is the chemical symbol of element, $Z =$ atomic number and A is atomic mass number. For example : Nuclide of gold ${ }_{79} A u^{197}$ in which 197 nucleons, 79 protons and 118 neutrons are there.
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