Question
Define the different terms used for the composition of a nucleus.
✓
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.
(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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