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(i) A radioactive nucleus ‘A’ undergoes a series of decays as given below : Aoverset(alpha)(to)A_(1)overset(beta)(to)A_(2)overset(alpha)(to)A_(3)overset(gamma)(to)A_(4) The mass number and atomic number of A_(2) are 176 and 71 respectively. Determine the mass and atomic numbers of A_(4) and A. (ii) Write the basic nuclear processes underlying beta^(+) and beta^(-) decays. |
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Answer» Solution :(i) As per DECAY series, mass number and atomic numbers of various nuclei are : `" "_(72)^(180)Aoverset(alpha)(to)" "_(70)^(176)A_(1)overset(BETA^(-))(to)" "_(71)^(176)A_(2)overset(alpha)(to)" "_(69)^(172)A_(3)overset(GAMMA)(to)" "_(69)^(172)A_(4)^(*)` Therefore, mass number of `A_(4)` is 172 and its atomic number is 69. Similarly, mass number of A is 180 and its atomic number is 72. (ii) At the time of `beta^(-)` emission, a neutron inside a nucleus decays as `" "_(0)^(1)n to " "_(+1)^(1)p +" "_(-1)^(0)e + bar(NU)` (antineutrino) At the time of `beta(+)` decay, a proton inside nucleus decays as : `" "_(+1)^(1)pto " "_(0)^(1)n + " "_(+1)^(0)e + nu` (neutrino) Neutrino as well as antineutrino are neutral particles with very little or no mass. |
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