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प्रश्न
When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom ______.
पर्याय
do not change for any type of radioactivity.
change for α and β radioactivity but not for γ-radioactivity.
change for α-radioactivity but not for others.
change for β-radioactivity but not for others.
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उत्तर
When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom change for α and β radioactivity but not for γ-radioactivity.
Explanation:
| Features | α- particles | β- particles | γ-rays | |
| 1. | Identity | Helium nucleus or doubly ionised helium atom (2He4) | Fast moving electron (–β0 or B–) |
Photons (E.M. waves) |
| 2. | Charge | + 2e | – e | Zero |
| 3. | Mass | 4 mp (mp = mass of proton) = 1.87 × 10–27 |
me | Massless |
| 4. | Equation of decay |
\[\ce{_{Z}X^A ->[α-decay]}\] \[\ce{_{z-2}Y^{A-4} + _{2}He^4}\] \[\ce{n_α = A - A^{'}/4}\] |
\[\ce{_{z}X^A -> _{z + 1} Y^A + _{-1}e^0 + {v}}\] \[\ce{_{z}y^A ->[n_{β}] z^' X^A}\] ⇒ nβ = (2nα = – Z + Z') |
\[\ce{_{Z}X^A -> _{Z}X^α + γ}\] |
A /3-particle carries one unit of negative charge (– e), an α-particle carries 2 units of positive charge (+ 2e) and γ (particle) carries no charge. Hence electronic energy levels of the atom charge for α and β decay, but not for γ-decay.
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