Current Affairs JEE Main & Advanced

Category : JEE Main & Advanced

The process by which the identity of a nucleus is changed when it is bombarded by an energetic particle is called nuclear reaction. The general expression for the nuclear reaction is as follows.

\[\underset{(\text{Parent nucleus)}}{\mathop{X}}\,+\underset{(\text{Incident particle)}}{\mathop{a}}\,\xrightarrow{\,}\]

\[\underset{\text{(Compound nucleus)}}{\mathop{C}}\,\,\xrightarrow{\,}\underset{(\text{Compound nucleus)}}{\mathop{Y}}\,+\underset{\text{(Product particles)}}{\mathop{b}}\,+\underset{(\text{Energy)}}{\mathop{Q}}\,\]

Here X and a are known as reactants and Y and b are known as products. This reaction is known as (a, b) reaction and can be represented as X(a, b) Y

(1) Q value or energy of nuclear reaction : The energy absorbed or released during nuclear reaction is known as Q-value of nuclear reaction.

Q-value = (Mass of reactants ? mass of products)\[{{c}^{2}}\] Joules

= (Mass of reactants ? mass of products) amu

If \[Q<0,\] The nuclear reaction is known as endothermic. (The energy is absorbed in the reaction)

If \[Q>0,\] The nuclear reaction is known as exothermic (The energy is released in the reaction)

(2) Law of conservation in nuclear reactions

(i) Conservation of mass number and charge number : In the following nuclear reaction

\[_{2}H{{e}^{4}}+{{\,}_{7}}{{N}^{14}}\to {{\,}_{8}}{{O}^{17}}+{{\,}_{1}}{{H}^{1}}\]

Mass number (A)\[\to \]         Before the reaction   After the reaction                                                  

       4 +14 = 18              17 + 1 = 18

Charge number (Z) \[\to \]  2 + 7 = 9                    8 + 1 = 9

(ii) Conservation of momentum : Linear momentum/angular momentum of particles before the reaction is equal to the linear/angular momentum of the particles after the reaction. That is \[\Sigma p=0\]

(iii) Conservation of energy : Total energy before the reaction is equal to total energy after the reaction. Term Q is added to balance the total energy of the reaction.

(3) Common nuclear reactions : The nuclear reactions lead to artificial transmutation of nuclei. Rutherford was the first to carry out artificial transmutation of nitrogen to oxygen in the year 1919.

\[_{2}H{{e}^{4}}+{{\,}_{7}}{{N}^{14}}\to {{\,}_{9}}{{F}^{18}}\to {{\,}_{8}}{{O}^{17}}+{{\,}_{1}}{{H}^{1}}\]

It is called \[(\alpha ,\,\,p)\] reaction. Some other nuclear reactions are given as follows.

\[(p,\,n)\] reaction  \[\Rightarrow \]               \[_{1}{{H}^{1}}+{{\,}_{5}}{{B}^{11}}\to {{\,}_{6}}{{C}^{12}}\to {{\,}_{6}}{{C}^{11}}+{{\,}_{0}}{{n}^{1}}\]

\[(p,\,\,\alpha )\]reaction  \[\Rightarrow \]\[_{1}{{H}^{1}}+{{\,}_{3}}L{{i}^{11}}\to {{\,}_{4}}B{{e}^{8}}\to {{\,}_{2}}H{{e}^{4}}+{{\,}_{2}}H{{e}^{4}}\]

\[(p,\,\,\gamma )\] reaction  \[\Rightarrow \]\[_{1}{{H}^{1}}+{{\,}_{6}}{{C}^{12}}\to {{\,}_{7}}{{N}^{13}}\to {{\,}_{7}}{{N}^{13}}+\gamma \]

\[(n,\,\,p)\] reaction \[\Rightarrow \]\[_{0}{{n}^{1}}+{{\,}_{7}}{{N}^{14}}\to {{\,}_{7}}{{N}^{15}}\to {{\,}_{6}}{{C}^{14}}+{{\,}_{1}}{{H}^{1}}\]

\[(\gamma ,\,n)\] reaction \[\Rightarrow \]\[\gamma +{{\,}_{1}}{{H}^{2}}\to {{\,}_{1}}{{H}^{1}}\,+{{\,}_{0}}{{n}^{1}}\]