JEE Main & Advanced Physics Nuclear Physics And Radioactivity Types of Nuclei

The nuclei have been classified on the basis of the number of protons (atomic number) or the total number of nucleons (mass number) as follows

(1) Isotopes : The atoms of element having same atomic number but different mass number are called isotopes. All isotopes have the same chemical properties. The isotopes of some elements are the following

\[_{1}{{H}^{1}},\,{{\,}_{1}}{{H}^{2}},\,{{\,}_{1}}{{H}^{3}}\] \[_{8}{{O}^{16}},\,{{\,}_{8}}{{O}^{17}},\,{{\,}_{8}}{{O}^{18}}\] \[_{2}H{{e}^{3}},\,{{\,}_{2}}H{{e}^{4}}\]  \[_{17}C{{l}^{35}},\,{{\,}_{17}}C{{l}^{37}}\]    \[_{92}{{U}^{235}},\,{{\,}_{92}}{{U}^{238}}\]

(2) Isobars : The nuclei which have the same mass number (A) but different atomic number (Z) are called isobars. Isobars occupy different positions in periodic table so all isobars have different chemical properties. Some of the examples of isobars are

\[_{1}{{H}^{3}}\,\text{and }{{\,}_{2}}H{{e}^{3}},\,\,\,\,\,\,{{\,}_{6}}{{C}^{14}}\,\text{and}{{\,}_{\text{7}}}{{N}^{14}},\,{{\,}_{8}}{{O}^{17}}\,\text{and }{{\,}_{9}}{{F}^{17}}\]

(3) Isotones : The nuclei having equal number of neutrons are called isotones. For them both the atomic number (Z) and mass number (A) are different, but the value of (A - Z) is same. Some examples are

\[_{4}B{{e}^{9}}\,\text{and}{{\,}_{5}}{{B}^{10}},{{\,}_{6}}{{C}^{13}}\,\text{and}{{\,}_{7}}{{N}^{14}},{{\,}_{8}}{{O}^{18}}\text{ and}{{\text{ }}_{9}}{{F}^{19}}\]

\[{{\,}_{3}}L{{i}^{7}}\,\text{and }{{\,}_{\text{4}}}B{{e}^{8}},{{\,}_{1}}{{H}^{3}}\,\text{and}{{\,}_{\text{2}}}H{{e}^{4}}\]

(4) Mirror nuclei : Nuclei having the same mass number A but with the proton number (Z) and neutron number (A ? Z) interchanged (or whose atomic number differ by 1) are called mirror nuclei for example.

\[_{1}{{H}^{3}}\,\text{and}{{\,}_{\text{2}}}H{{e}^{3}},\,{{\,}_{3}}L{{i}^{7}}\,\text{and}{{\text{ }}_{\text{4}}}B{{e}^{7}}\]