JEE Main & Advanced Chemistry Surface & Nuclear Chemistry / भूतल और नाभिकीय रसायन Artificial Transmutation Of Elements

The conversion of one element into another by artificial means, i.e., by means of bombarding with some fundamental particles, is known as artificial transmutation. The phenomenon was first applied on nitrogen whose nucleus was bombarded with a-particles to produce oxygen.

\[\underset{\text{Nitrogen isotope}}{\mathop{_{7}{{N}^{14}}}}\,+\,\underset{\text{Alpha particle}}{\mathop{_{2}H{{e}^{4}}}}\,\to \,\underset{\text{Oxygen isotope}}{\mathop{_{8}{{O}^{17}}}}\,+\,\underset{\text{Proton}}{\mathop{_{1}{{H}^{1}}}}\,\]

The element, which is produced, shows radioactivity, the phenomenon is known as Induced radioactivity. The fundamental particles which have been used in the bombardment of different elements are,

a-particle : \[_{2}H{{e}^{4}}\] ; Proton : \[_{1}{{H}^{1}}\]

Deutron : \[_{1}{{H}^{2}}\] or \[_{1}{{D}^{2}}\] ; Neutron : \[_{0}{{n}^{1}}\]

Since a-particles, protons and deutrons carry positive charge, they are repelled by the positively charged nucleus and hence these are not good projectiles. On the other hand, neutrons, which carry no charge at all, are the best projectiles. Cyclotron is the most commonly used instrument for accelerating these particles. The particles leave the instrument with a velocity of about 25,000 miles per second. A more recent accelerating instrument is called the synchrotron or bevatron. It is important to note that this instrument cannot accelerate the neutrons, being neutral.

When a target element is bombarded with neutrons, product depends upon the speed of neutrons. Slow neutrons penetrate the nucleus while a high-speed neutron passes through the nucleus.

\[_{92}{{U}^{238}}+\,\underset{\text{slow speed}}{\mathop{_{0}{{n}^{1}}}}\,\to {{\,}_{92}}{{U}^{239}};{{\ }_{92}}{{U}^{238}}+\,\underset{\text{high speed}}{\mathop{_{0}{{n}^{1}}}}\,\to {{\,}_{92}}{{U}^{237}}+\,{{2}_{0}}{{n}^{1}}\]

Thus slow neutrons, also called thermal neutrons are more effective in producing nuclear reactions than high-speed neutrons.

Alchemy : The process of transforming one element into other is known as alchemy and the person involved in such experiments is called alchemist. Although, gold can be prepared from lead by alchemy, the gold obtained is radioactive and costs very high than natural gold.

(i) Transmutation by a-particles

(a)                a, n type

\[_{4}B{{e}^{9}}(\alpha ,\,n){{\,}_{6}}{{C}^{12}}\] i.e. \[_{4}B{{e}^{9}}+{{\,}_{2}}H{{e}^{4}}\to {{\,}_{6}}{{C}^{12}}+{{\,}_{0}}{{n}^{1}}\]

\[_{94}P{{u}^{239}}\,(\alpha ,\,n){{\,}_{96}}C{{m}^{242}}\]i.e. \[_{94}P{{u}^{239}}+{{\,}_{2}}H{{e}^{4}}\to {{\,}_{94}}C{{m}^{242}}+{{\,}_{0}}{{n}^{1}}\]

(b) a, p type

\[_{9}{{F}^{19}}\,(\alpha ,\,p){{\,}_{10}}N{{e}^{22}}\] ie.\[_{9}{{F}^{19}}+{{\,}_{2}}H{{e}^{4}}\to {{\,}_{10}}N{{e}^{22}}+{{\,}_{1}}{{H}^{1}}\]

\[_{7}{{N}^{14}}\,(\alpha ,\,p){{\,}_{8}}{{O}^{17}}\] i.e.,  \[_{7}{{N}^{14}}+{{\,}_{2}}H{{e}^{4}}\to {{\,}_{8}}{{O}^{17}}+{{\,}_{1}}{{H}^{1}}\]

(c) a, b type

\[_{26}F{{e}^{59}}\,(\alpha ,\,\beta ){{\,}_{29}}C{{u}^{63}}\] i.e., \[_{26}F{{e}^{59}}+{{\,}_{2}}H{{e}^{4}}\to {{\,}_{29}}C{{u}^{63}}+{{\,}_{-1}}{{e}^{0}}\]

(ii) Transmutation by protons

(a) p, n type

\[_{15}{{P}^{31}}\,(p,\,n){{\,}_{16}}{{S}^{31}}\]  i.e., \[_{15}{{P}^{31}}+{{\,}_{1}}{{H}^{1}}\to {{\,}_{16}}{{S}^{31}}+{{\,}_{0}}{{n}^{1}}\]

(b) p, g type

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

(c) p, d type

\[_{4}B{{e}^{9}}\,(p,\,d){{\,}_{4}}B{{e}^{8}}\]  i.e., \[_{4}B{{e}^{9}}+{{\,}_{1}}{{H}^{1}}\to {{\,}_{4}}B{{e}^{8}}+{{\,}_{1}}{{H}^{2}}\]

(d) p, a type

\[_{8}{{O}^{16}}\,(p,\,\alpha ){{\,}_{7}}{{N}^{31}}\]  i.e., \[_{8}{{O}^{16}}+{{\,}_{1}}{{H}^{1}}\to {{\,}_{7}}{{N}^{13}}+{{\,}_{2}}H{{e}^{4}}\]

(iii) Transmutation by neutrons

(a) n,p type

\[_{13}A{{l}^{27}}\,(n,\,p){{\,}_{12}}M{{g}^{27}}\] i.e., \[_{13}A{{l}^{27}}+{{\,}_{0}}{{n}^{1}}\to {{\,}_{12}}M{{g}^{27}}+{{\,}_{1}}{{H}^{1}}\]

(b) n,a type

\[_{8}{{O}^{16}}\,(n,\,\alpha ){{\,}_{12}}M{{g}^{27}}\] i.e., \[_{8}{{O}^{16}}+{{\,}_{0}}{{n}^{1}}\to {{\,}_{6}}{{C}^{13}}+{{\,}_{2}}H{{e}^{4}}\]

(c) n, g  type

\[_{92}{{U}^{238}}\,(n,\,\lambda ){{\,}_{92}}{{U}^{239}}\] i.e., \[_{92}{{U}^{238}}+{{\,}_{0}}{{n}^{1}}\to {{\,}_{92}}{{U}^{238}}+\,\lambda \]

(d) n,b type

\[{{\,}_{8}}{{O}^{18}}\,(n,\,\beta ){{\,}_{9}}{{F}^{19}}\] i.e., \[{{\,}_{8}}{{O}^{18}}+{{\,}_{0}}{{n}^{1}}\to {{\,}_{9}}{{F}^{19}}+{{\,}_{-1}}{{e}^{0}}\]

(iv) Transmutation by deutrons

(a)                d,p type

\[_{3}L{{i}^{6}}\,(d,\,p){{\,}_{3}}L{{i}^{7}}\]i.e.,\[_{3}L{{i}^{6}}+{{\,}_{1}}{{H}^{2}}\to {{\,}_{3}}L{{i}^{7}}+{{\,}_{1}}{{H}^{1}}\]

\[_{32}A{{s}^{75}}\,(d,\,p){{\,}_{32}}A{{s}^{76}}\] i.e., \[_{32}A{{s}^{75}}+{{\,}_{1}}{{H}^{2}}\to {{\,}_{32}}A{{s}^{76}}+{{\,}_{1}}{{H}^{1}}\]

(v) Transmutation by g-radiations

(a) g, n type

\[_{4}B{{e}^{9}}\,(\lambda ,\,n){{\,}_{4}}B{{e}^{8}}\] i.e., \[_{4}B{{e}^{9}}+\gamma \to {{\,}_{4}}B{{e}^{8}}+{{\,}_{0}}{{n}^{1}}\]

Synthetic elements : Elements with atomic number greater than 92 i.e. the elements beyond uranium in the periodic table are not found in nature like other elements. All these elements are prepared by artificial transmutation technique and are therefore known as transuranic elements or synthetic elements.