Decay of $_{92}U^{235}$ is $...$ order reaction.

$A$ radioactive isotope has a half-life of $20 \ days$. If $100 \ g$ of the substance is taken,the weight of the isotope remaining after $40 \ days$ is ......... $g$.

$_{11}Na^{24}$ has a half-life of $15 \ h$. On heating,its half-life will:

The decay of $_{92}U^{235}$ is a reaction of .......... order.

$A$ certain nuclide has a half-life period of $30 \ min$. If a sample containing $600$ atoms is allowed to decay for $90 \ min$,how many atoms will remain (in $atoms$)?

The half-life of a radioisotope is $20 \ hours$. After $60 \ hours$,what fraction of the initial amount will remain?