The $\beta$-particles of a radioactive metal originate from

A nucleus of an element ${}_{84}{X^{202}}$ emits an $\alpha $-particle first, $\beta $ -particle next and then a gamma photon. The final nucleus formed has an atomic number

Explain $\beta -$ decay and how does a radioactive nucleus emit $\beta -$ particles, even if there are no $\beta -$ particles in the nucleus ? Here why does radioactive nuclide not change during beta emission ? 

In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following would be emitted in the decay process

In which of the following nuclear reactions, the product is incorrectly matched ?

In a reactor, $2\, kg$ of ${ }_{92} U ^{235}$ fuel is fully used up in $30$ days. The energy released per fission is $200\, MeV.$ Given that the Avogadro number, $N =6.023 \times 10^{26}$ per kilo mole and $1\, eV =1.6 \times 10^{-19}\, J .$ The power output of the eactor is close to$.....MW$