Stability of Nucleus

The ratio of the $\left(\frac{\mathrm{e}}{\mathrm{m}}\right)$ (specific charge) values of a electron and an $\mathrm{\alpha }-$particle is

A new radionucleide is obtained from the radionucleide ${ }_{\text{90}}^{\text{234}}\mathrm{T}\mathrm{h}$ through two successive $\mathrm{\beta }$ -decays followed by one $\mathrm{\alpha }$ -decay. The atomic number and the mass number respectively of the resulting radionucleide is

What is the binding energy (in J/mol or kJ/mol) of an electron in a metal, whose threshold frequency for photon electron is $2.5\times 10^{14}{\mathrm{s}}^{-1}$ ?

The isotope ${}_{92}^{238}\mathrm{U}$ decays successively to form ${}_{90}^{234}\mathrm{T}\mathrm{h},\mathrm{ }{}_{91}^{234}\mathrm{P}\mathrm{a},\mathrm{ }{}_{92}^{234}\mathrm{U},\mathrm{ }{}_{90}^{230}\mathrm{T}\mathrm{h}$ and ${}_{88}^{226}\mathrm{R}\mathrm{a}$ , The radiations emitted in these five steps are

A first order reaction takes 40 min for $30\mathrm{\%}$ decomposition, the t_1/2 value will be

If $8$ g of a radioactive isotope has a half-life of $10$ hrs, then the half-life of $2$g of the same substance is

In nuclear reaction,

${}_3{}^7\mathrm{L}\mathrm{i}+\mathrm{ }{}_1{}^1\mathrm{H}\mathrm{ }\to 2{}_2{}^4\mathrm{H}\mathrm{e}$

The mass loss is nearly 0.02 amu. Hence, the energy released (in units of million kcal/mol) in the process is approximately

Identify the wrong statement.

The minimum energy of 1 photon that can produce an electron - positron pair is :